Change Resolution Problem

Hello, I am using version 2021.3.20f1. When I change the resolution with Screen.SetResolution, the quality of texts etc. decreases. In this case, when I switch to window mode with ALT + Enter and make it full screen again, it gets better. What could be the reason?
And when i supported every aspect ratios, in game screen I have black bars both of right and left side.

Hello, I have solved the problem and I am sharing the solution in case it can help.

I was doing the resolutions with dropdown and Resolution class. However, instead of pulling the Resolution value and doing Screen.SetResolution(resolution.width, resolution.height, true); it gets better when I manually do Screen.SetResolution(1920, 1080, true);.

Even though I converted resolution.width and resolution.height variables with Convert.ToInt32 and tried again, it had no effect. It doesn’t work unless I enter it manually, I couldn’t figure out why.