Whenever I connect my Ps4 controller with Ds4 Windows via Bluetooth to my laptop, my Internet (only on the laptop) suddenly becomes extremely bad. How does this come about and what can I do about it?
The problem is that Bluetooth uses the same frequency as the WLAN. So 2.4 GHz. This will disrupt it.
If you have dual band Wi-Fi (Wi-Fi hardware in your laptop), you should change the Wi-Fi frequency to 5 GHz: https://www.tutonaut.de/anleitung-5-ghz-wlan-auf-windows-pcs-bevorzugen/ Then 5 GHz is used for Wi-Fi if possible. If the WLAN hardware in the laptop does not support 5 GHz, 2.4 GHz is used automatically.