Very low fps on a normal graphics card

I bought a computer on avito with the following configuration: CRU: Intel Soge i3 2100 Video card: Nvidia GTS 450 on 1gb Mat. board: ASUS P8P67 LE RAM: 4GB DDR3 It was running Windows 10. We have installed ubuntu 20.04. The problem is as follows: very low fps even when playing videos from youtube. If you take a window and pull on the screen, you will see horizontal stripes-cuts, "frame joints". When testing with the help of glxgears, it writes 40-55 fps to the full screen, but it looks like it's 15 fps. I also noticed the following effect: in places on the screen where there is a sharp transition between black and white, where inter-pixel anti-aliasing should be used as much as possible, there is a thin strip (1 pix wide) of some noise, snow as if. You can see it very poorly and it does not interfere with life at all, but perhaps this indicates that the seller slipped a semi-damaged video card. This noise was also present in Windows. There was also such a problem: the computer does not work I did not want to determine the real resolution of the monitor and showed everything in a very low resolution, but this was solved by changing the default resolution in /etc/default/grub to the real resolution of the monitor. Resolution: 1280x1024 pix. Whether there were problems with fps in Windows-I do not know. If you have any suggestions on what's wrong with fps, please write. Or maybe this is the norm for my graphics card?