Alt-Tab and FPS issue

[Alt-Tab and FPS issue]

Hello, I am looking for solutions about 2 problems.

 1st problem :

When Alt-Tabbing or try to change the graphic settings, a black screen appears. I've tried all the solution suggestions but the problem still exists.

-I did everything have mentioned here : 

 The problem still exists.

- I did all the suggestions here: 

I've activated "windowfullscreen" in "SystemOptionGraphics.cfg" file and now, I can alt-tabbing but still cannot change options and use some in-game contents. 

 The problem only exists in this game and one of my friends have the same problem(he has the same system as mine)

CPU:Ryzen 3600x  GPU: 5600xt RAM:16gb ,win10

2nd problem: 

FPS is always "60" but  "Fixed FPS"  option is not marked.

Thanks in advance.