How do I get my old internet speed back on my PC?

Good day,

I have the problem that my PC can no longer access the internet speeds it used to have.

It was about 200mbits before and suddenly it's fluctuating between 9-70.

Everything has become really slow and I don't know why.

It's not the WiFi's fault because my phone can still access the 200.

I have installed a WLAN card, namely the

Asus PCE-AC68 motherboard Asrock x570 Extreme4

Switching to LAN is not an option.

Thank you for your efforts