Why can't I restart db? For some reason it does not work, although the status says running(

This should work:

fly postgres restart -a astrumsoft-db

backend ‘bk_db’ has no server available!
Our database is constantly crashing. What is the problem?

Hello. The volume where postgres data is stored has reached +90% usage, the database switched to read-only mode. See the output of fly checks list -a astrumsoft-db

How can I exit read only mode? I need to connect to a database to save data from there, after which I will increase the RAM to 1 GB by paying for a new VM for a month.

See Volumes · Fly Docs