On 000webhost there are tools that you can run to fix ownership and permission.
The tools are 'Fix File Ownership' and 'Fix File Permissions' from your control panel. These tools will recreate your public_html directory and fix any ownership and permission issue.
After you do that above and still have an error then you will likely to have bad .htaccess, rename it is the easiest and quickest to see if this is the cause then figure out how to write correct rewrite rule after your site load without any error.
If all else fail then you need to reset and reload your account from your CPanel on that particular domain name.