Internal Error 500 after trying finalize the back ofice installation

[Marians2002]

Hi Guys,

I have trouble with the installation of PS 1.7.7.2 which stuck after I want to setup the Back Office and finish the installation. 

I search the advises online, so I did check the version of PHP which I set to 7.4 (I did even try 7.3, 7.2, 7.1), I also did try to change chmod to 644, 700, 755 of index.php file in "install" folder but with the same result. Unfortunately, I'm not the IT expert... But I did successful PS installations before by myself. I'm pretty frustrated that I cannot handle it as it is advised by other users. Can you please tell me what I'm doing wrong?

Thank you very much

Marian