update link for fritz app wlan

Signed-off-by: Simon L. <[email protected]>

docs/improve-performance.md

@@ -13,7 +13,7 @@ First of all, here are some general network advices that I've followed which hel
 For DSL connections is currently (24.03.2021) the [FRITZ!Box 7530 AX](https://geizhals.eu/avm-fritz-box-7530-ax-a2411180.html?hloc=at&hloc=de&hloc=eu&hloc=pl&hloc=uk) recommended
 - Also make sure, that you connect to your router via the 5 GHz network and not 2.4 GHz network <br/>
 (Usually, you can e.g. give the different frequencies a different name in your routers GUI. By doing so, you can make sure that your devices get always connected to the correct network)
-- If your appartment/house is too big for the 5 GHz network for a complete and speedy coverage (for debugging purposes, you can use e.g. the [FRITZ!App WLAN](https://en.avm.de/products/fritzapps/fritzapp-wlan). A good rule of thumb is that you need a repeater if the 2.4 GHz speed exceeds the 5 GHz speed in rooms that need to get covered by Wi-fi), you should buy a Wi-fi repeater also with Wi-fi 5 or Wi-fi 6 that should get connected to your router via an ethernet cable (hence the repeater needs an ethernet port to be able to do that)<br/>
+- If your appartment/house is too big for the 5 GHz network for a complete and speedy coverage (for debugging purposes, you can use e.g. the [FRITZ!App WLAN](https://en.avm.de/products/apps/fritzapp-wi-fi/). A good rule of thumb is that you need a repeater if the 2.4 GHz speed exceeds the 5 GHz speed in rooms that need to get covered by Wi-fi), you should buy a Wi-fi repeater also with Wi-fi 5 or Wi-fi 6 that should get connected to your router via an ethernet cable (hence the repeater needs an ethernet port to be able to do that)<br/>
 Recommended is currently (24.03.2021) the [FRITZ!Repeater 2400](https://geizhals.eu/avm-fritz-repeater-2400-20002855-a2082185.html)<br/>
 (Please note that you might be able to achieve a better Wi-fi coverage of your appartment/house by moving the router to a better place where it covers more rooms before buying additional Wi-fi repeaters)
 - Your server should be directly connect to your router via an ethernet cable. Make sure that you use at least a Gbit ethernet cable for this, it must at least match the speed of the ethernet port on your server and router. (The same applies to Wi-fi repeaters that I've mentioned above)<br/>