I'm impressed that you did this as your first Godot game! It was a lot of fun and I really enjoyed it. I played it all the way through.
One suggestion would be to make it easier to do multiple things at once, since it felt like as soon as a drone saw me I was done. I ended up doing well by "planning", that is inching forward till they were on the edge of the screen, locking on, setting the turrets and then approaching to within range. I wasn't sure if that was as designed, or a cheese move. It would have been nice I think, to make it easier to move and shoot. Something like have left button always move and right button always lock on and lock on starts firing by default.