How to manage example.com website from admin.example.com

Hey, 
I'd like to ask if it's possible to manage files, folders etc. of the main domain (example.com) from subdomain (e.g.: admin.example.com).

I want to create (folders, upload files etc.) in the main domain but i can't while i get a 505 error.

Have you faced anything like that? How did you solve it?

Thanks!

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