Sorry to hear about this. Please try switching the Renderer to Mercury Playback Engine Software Only and check if it's working properly. Also, please check if there is any driver update available for the GPU installed on your system. Hope it helps.
The problem was the GPU as you said but the core issue is the premier pro 2020 version 14.0 so i have downgraded to 2019 and it works fine now. I hope they resolve the issue of the 2020 14.0 version compatability with the Radeon rx 5700xt