Safari networking process high CPU (over 200)

Hi there.

Since a few days I experience high CPU load on the process "safari networking" when I open twitch.tv and watch streams. First it works and after 5 to 8 minutes the process "safari networking" goes to over 200 CPU load and then freezes. After stopping the safari and restarting the browser it works newly for 5 minutes than freezes again. No problems with firefox.

I cleared cookies, history and ~/Library/Safari. Tried also CleanMyMac X. None of those solutions worked.

No extensions installed.

Safari Version 14.0.3 (16610.4.3.1.7)

Mac OS BigSur 11.2.3 (20D91)

Connectet via LAN cable.

Thanx in advance for you help.