I accidentally installed OSClass over my Oxwall Installation, so after I uninstalled it it now says 404 Not Found. How do I fix this, and bring it back to the original Oxwall website?
Softaculous must have asked you if you want to overwrite files when you installed Osclass over your Oxwall installation. Only if you selected the checkbox Overwrite files then Softaculous will install it.
When you install OSClass over Oxwall it will overwrite the common files in Oxwall and Osclass i.e. index.php, etc and when you removed the Osclass installation it removed the Osclass files and the common ones like index.php hence you Oxwall installation does not work now due to missing file.