I failed to find a solution regarding VS2017. Even formatting the computer didn’t help.
It was fine to use VS2015 and Qt Creator is also working just fine, but not VS2017. I am just a ■■■■■■ for changing to VS2017 this fast. I should have waited a bit longer…
I guess I will stick with Qt Creator. It would have been better to use both at the same time like I did before, but whatever… Anyways, thanks for helping me Matthias Hölzl.
By the way, I have a few things to say to Microsoft.
Dear Microsoft
If there is a language selection for a program. Please make it so that the installer' language also changes, not just the installation' language.
P.S.: There will always be translation errors around. Don't forget that.