How to set an external display as the main one in a macbook, in the EFI firmware itself?

Question

macbook

Good afternoon or evening.
Problem! Please help, I don't know what.
They gave me a white macbook 7.1 with a broken screen, I took it off, connected an external monitor with an adapter. Minidisplay adapter to DVI. There was such a problem.
Sometimes it turns on and the screen resolution is Full HD (Full HD Monitor), and sometimes 800x600 or something like that, but when it's not full HD, it just doesn't load further than the apple.
How can I tell the firmware that there is such a monitor and it is the main one.
It feels like the firmware of the roofing felts does not always detect an external monitor, or it thinks that the built-in one is still there, I can’t understand what’s wrong and how to fix it.
Tired of constantly rebooting SMC and PRAM, and by the way this does not help
Please help