Ubuntu Mate 20.04 LTS Display Problem

I want to run my Rasperry Pi 4 on my tv(lg 65un71006lb). Everything is working fine, but i cant set the resolution.

Its stuck at 1024x768.

I tryed xrandr
cvt 3840 2160
xrandr --newmode "MyMode" (stuff from above)
xrandr --addmode Virtual1 "MyMode"

When i select the Resolution of the Display settings, theres "CRTC 63 Error".

Someone got for me a solution?