Ok I changed some graphi settings and GPU is now much lower at around 40%.

Laggs are still there however unfortunately.

In my wifi I split between 5ghz and 2,4gz and was logged in into the 5ghz until now.
I switched to 2,4ghz now and it seems I dont have that much lagg anymore.
Does anybod know that 5ghz could cause issues with multiboxxing?