you have a permission problem at the server level so Concrete5 can't access required files.

Make sure that folder is writable and has the proper CHMOD value.

The CHMOD value for the whole application/config folder and all it's subfolders and files should be 755

You can read this article about it:https://documentation.concrete5.org/developers/installation/installa...

If you're not sure how to do that, your host probably has a tutorial or can show you the steps to do it. It also can usually be done easily from your cPanel interface.