Okay, so I don't know what I did, but I know that I didn't delete anything. The last thing I remember doing was changing what the URL of the homepage was and then my site lost all CSS structure and themes.
I figured, after some time of fiddling with it, that I would just try to install the new version and overwrite any problems. That didn't work.
Now I also get problems saying that my databse is out of date and I still don't have any CSS styles or structure.
I need some serious help here!