proxy changing maleware

I have valid avast premier and grimefighter licences, but some maleware has infected my pc.
It keeps changing the proxy so my internet access gets super slow. When I manually turn off the proxy tunnel, something keeps changing it back

I have run full scan on my computer and grimefigher twice, but the issue hasn’t be solved…
Can someone please advise me what to do?

https://forum.avast.com/index.php?topic=53253.0