Can Firefox not reinstall because profile is no longer there?

I wanted to clean Firefox today because it started so slowly. In the middle of the cleanup but my laptop was hung up and I had to restart it. Now I could not start Firefox with the error message "Your profile Firefox can't be loaded, it may not be available or you can't access it."

I then stupidly deleted Firefox first and tried to download it again - with the same result.

In the support pages of Mozilla I found a problem solution where I find my Firefox profile. It's available. But as a precaution, I saved all the content in a new profile folder.

Nevertheless it stays that way - I can neither install nor start Firefox.

Can anyone help me?

Rebuild Windows.