I assume you’re deleting via FTP/SSH rather than WordPress itself?
The good news here is that it seems to just be the WordPress files that you’ve deleted, so your posts etc should all be safe in the database.
I’d recommend taking a backup of the database now, to be safe, you can usually do this via phpMyAdmin or your hosts control panel.
Then contact them and see if they have an older version of your files. The original error usually refers to white-space in the code (i.e. extra spaces where there shouldn’t be any)