I am not much of a sysadmin either and have had to get help from some other instance admins in the past. Here is the exact process I go through to manually make and then restore a backup. I don't have this automated since I just work in dev environments, but you could put this in a shell script and schedule it with cron or something like that.

Here is how I make the backup (pgdata folder in my case):

# Prerequisite: navigate to the pyfedi folder

# Shut down the docker containers
docker compose down

# Wait for the containers to shut down...

# Then make the backup of the db volume
sudo rsync -a pgdata/ pgdata_backup

And here is how I restore the backup if I mess up my db:

# Again, need to be in the pyfedi folder

# Shut down the docker containers
docker compose down

# Wait for the containers to shut down...

# Delete the messed up db folder
sudo rm -r pgdata

# Rename the backup folder to swap it back in
sudo mv pgdata_backup pgdata

# Start the containers back up
docker compose up -d