I changed my backend to SQL and restarted the server but it whent back to file and it now only works when the server is active and i manually set the backend to sql with "pex backend sql". It doenst go to SQL automatically on startup. What to do?!

Running that command only changes the backend for the current server run. For a permanent change, you have to edit the config.yml to change the active backend.

I changed it in de config but when restarting the node it adds the file at the bottom of the backend under the sql backend and doesnt follow the sql backend