how can i fix this problem?
HTTP 502

Web server temporarily unavailable

pls helm me

and also when I go to online file manager it writes this:

This site can’t be reached refused to connect.
Search Google for index

Well, you could start by actually including your URL so we can check stuff rather than just guess.

Both your website for and the file manager work fine from my end.

For the file manager, please try if you can access it through another internet connection as well. Some (bad) internet provider indiscriminately block access to some of our services and there is not much we can do against that.