Site moved to main directory with functions.php

I have developed a website in a sub folder (domain.com/newsite) of the domain and then I had to move it to the main root so I just specified into the file functions.php the new site url and then I copied the files and directories on the root.
Now I can see the site correctly on domain.com but the problem is that if I delete the folder “newsite”, I get a 500 error and the site doesn’t display anymore…
So, there’s something wrong… Any suggestion??
Thanks in advance