note: You can't run this site locally, because of proprietary backend, but you can preview the html file preview.html for styling css.
There are various way you can contribute to this project. Refactoring writings, updating css, Adding Language support etc. We will cover them one by one.
There is app.css file which is the main stylesheet. Use preview.html to view the rendered html file. This will help you style the website.
Use the english.tr as a reference to add your translation to this project.