[CONTENT] Teacher manual improvements NL EN (#4425)

The teacher manual is fully up to date again! :)

I would only like to add the answer account to it, but #4424 

Some tests might get angry because I've added some headers that will not exist yet in other languages. 
Weblock will definitely be angry, haha.

content/pages/ar.yaml

@@ -39,21 +39,54 @@ sections:
     subsections:
     -   title: "Tutorial"
         text: |
-            هل ترغب في متابعة البرنامج التعليمي (مرة أخرى)؟ انقر <a href="https://hedycode.com/tutorial" target="_blank">هنا</a>.
+            هل ترغب في متابعة البرنامج التعليمي (مرة أخرى)؟ انقر <a href="https://hedy.org/tutorial" target="_blank">هنا</a>.
 -   title: "Teaching preparations"
     key: "preparations"
     subsections:
+    -   title: "For teachers"
+        text: |
+            You can prepare your classes at the <a href="https://hedy.org/for-teachers" target="_blank">For Teachers page</a>. On this page you'll find everything you'll need to teach with Hedy, like your classes, your adventures and slides. All the functionalities of the for teachers page are explained below.
     -   title: "Creating a Class"
         text: |
             As a teacher, you can create a class for your students. In this class you can see the students' accounts and their programs and you could monitor their progress.
             This [video](https://www.youtube.com/watch?v=Y3RTIWftJQg) shows you how to quickly create a class in Hedy.
     -   title: "Customize your Class"
         text: |
-            You can also customize your class and choose which adventures are available for them. This way your students won't be overwhelmed by the amount of adventures and levels, and they can specifically focus on the adventures you'd like them to practice with.
-            This [video](https://www.youtube.com/watch?v=qva9gXBoUwY&t=10s) shows you how to customize your class.
+            You can customize your class and choose which adventures are available for your students. This way your students won't be overwhelmed by the amount of adventures and levels, and they can specifically focus on the adventures you'd like them to practice with.
+            Click on your class on the for teachers page and choose 'customize class'. On this page you can select levels, set opening dates, unlock level tresholds and more.
+
+            **Select and order adventures**
+            <img src="https://github.com/hedyorg/hedy/assets/80678586/df38cbb2-468e-4317-ac67-92eaf4212adc" width="1000">
+            In this section you can select and order adventures. The pink tabs are adventures with new commands. The gray tabs are regular adventures. To rearrange the order of the adventures, you can drag the tabs. However, we do advise you to use the regular order of adventures as the Hedy team made sure the adventures go from easiest to hardest.
+            If you want to remove an adventure for your students, simply click the cross on the adventure's tab.
+            <img src="https://github.com/hedyorg/hedy/assets/80678586/0ddd10b5-ef60-4480-a0c4-fc9a0f323baa" width="300">
+            If you want to add adventures, for instance your own adventure or an adventure you accidentally removed, use this menu to add the adventure to your students' adventures. Simply click the adventure you want to add and it (re)appears in the line of adventures. To undo all your changes to the adventures, click 'Reset'.
+
+            **Opening dates**
+            <img src="https://github.com/hedyorg/hedy/assets/80678586/4e59acfa-4772-429f-8328-babb43c942d5" width="300">
+            With this feature you can set open_ingdates for the levels. This way you can make a lesson plan before your course begins and not worry about opening new levels each week. In the image above the first level is opened directly, the second will open the 23th of september, and the 3rd level the week after. The other levels are closed.
+            Don't want to set opening dates? No problem, just leave this section blank.
+
+            **Unlock level tresholds**
+            <img src="https://github.com/hedyorg/hedy/assets/80678586/99a34dab-f112-459e-bfd1-07618be4715a" width = "1000">
+            This featue allows you to set a treshold for your students' quiz grade, before they can continue to the next level. For example, if you enter "80" your students have to score at least 80% on the quiz before they are allowed to go to the next level. If they haven't met the treshold, they are not allowed to continue and have to retake the quiz.
+            Don't want to use the treshold? No worries, just keep this section blank.
+
+
+            **Other settings**
+            <img src="https://github.com/hedyorg/hedy/assets/80678586/a8491d67-6d6e-42a7-b672-fd3d083a76f8"/>
+            There are some other setting that could be usefu to you aswell. Our first extra setting is 'Mandatory developer's mode'. In developers mode the students only see their input and output screens and the run button. The adventures are hidden and there are no cheatsheets available. This might come in handy in a test situation.
+            If this option is not selected the developer's mode is available for students too as a voluntairy option.
+
+            If you want all your students to be visible in de class highscore, you can select the second option.
+            With all the other options you can choose to hide some functions or content for your students, this might help them focus more.
+
+            **Save**
+            <img src="https://github.com/hedyorg/hedy/assets/80678586/df179df3-3073-4d15-bba6-62e58fb675be" width="300">
+            Don't forget to save your changes when you're done costumizing your class.
     -   title: "Student Accounts"
         text: |
-            There are 2 ways to let your students join your class: You can create accounts for them, or they could create their own accounts.
+            To add students to your class go to the class page by clicking in the class name on the 'for teachers' page. Then click 'add students'. There are 2 ways to let your students join your class: You can create accounts for them, or they could create their own accounts.
 
             **You create accounts for your students**
             The easiest way to add students to your class is by creating an account for them. This can be done by clicking the 'create student accounts' button and filling in the usernames and passwords for them.
@@ -105,7 +138,8 @@ sections:
             We use this structure in our lessons: Introduction, New concepts and commands, let's get to work, puzzels and quizzes.
     -   title: "Slides"
         text: |
-            **COMING SOON** Here you'll soon find slides to use in your lessons.
+            When giving instructions you might want to use our slides. Our slides are available on the 'For teachers' page. There is a set of slides for each level. In the slides all the new commands for that level are explained. We have aimed to explain why these changes are nessecary or how the new commands come in handy.
+            We also give some examples of how the new commands can be used. You could of course also use your own slides, or just open Hedy and show your students around the website. Whichever you prefer to give the best Hedy lessons!
     -   title: "Introduction"
         text: |
             You can start your lessons by activating your students' prior knowledge: What do they already know about the subject, what did they learn in the previous lesson and which mistakes did they make that they've now learned from?
@@ -115,7 +149,7 @@ sections:
             The new concepts and commands can be very hard for some students to fully understand.
             That's why it's of importance to model the proper use of the new commands to your students.
             Especially in the lower levels, where some students have no experience whith programming at all, it can be hard for them to understand the new abstract concepts.
-            Showing a lot of examples makes an abstract concept (for instance: 'What is a variable?') more recognizable and easier to understand ('Look, the variable pet changed into dog').
+            Showing a lot of examples makes an abstract concept (for instance: 'What is a variable?') more recognizable and easier to understand ('Look, the variable pet changed into dog'). Our slides could help you with that.
     -   title: "Let's get to work"
         text: |
             Each level contains different adventures that you can find in the pink tabs. The first pink tab explains the new commands in this level.
@@ -149,18 +183,18 @@ sections:
             It is also possible for teachers to create your own adventure. [This video](https://www.youtube.com/watch?v=A0zbXpxX4q4) shows you how to create your own adventure as a teacher and add it to your class(es).
     -   title: "Explore page"
         text: |
-            On the [explore](https://hedycode.com/explore) page you can view the work of other Hedy users. You can try out their programs and use them as inspiration to create something cool yourself.
+            On the [explore](https://hedy.org/explore) page you can view the work of other Hedy users. You can try out their programs and use them as inspiration to create something cool yourself.
             You can also add a program you've made to the explore page yourself by clicking 'Save and share code' in the coding screen or go to My Programs and click 'Share'.
             Don't want to share your work anymore? Simply go to 'My Programs' and click 'Unshare'.
             If you want more information about the explore page, check out this [video](https://www.youtube.com/watch?v=26boFjqvS5Q).
     -   title: "My achievements"
         text: |
-            If you click on your username in the topright corner of your screen, you can go to [My achievements](https://hedycode.com/my-achievements). On this page you achievements are collected. Your students have such a page as well.
+            If you click on your username in the topright corner of your screen, you can go to [My achievements](https://hedy.org/my-achievements). On this page you achievements are collected. Your students have such a page as well.
             When you hover over the badge with your mouse, you'll see how to earn the badge. There are hidden badges too, of which you'll have to find out yourself how to earn them.
             If you want more information on the achievements, check out this [video](https://www.youtube.com/watch?v=-FjmKejukCs).
     -   title: "High Scores"
         text: |
-            On [this page](https://hedycode.com/highscores) you can see the high scores of all Hedy users.
+            On [this page](https://hedy.org/highscores) you can see the high scores of all Hedy users.
             In this [video](https://www.youtube.com/watch?v=IqTiUkBVTo8) you can learn some more about the high scores.
     -   title: "Debugger"
         text: |