i deleted a part of the outline of the gameboy
Don't be afraid to start again Tristan. At the beginning you're going to make mistakes and most of the time it's quicker to start over than to try and fix what you already have, plus you gain speed. So just start from scratch and you'll notice that now you have gained experience points and you know what not to do.
If you make a mistake like this you can always press CTRL+Z to undo. The default undo steps is 36 if I remember correctly.
Perhaps you missed the Blender Basics, it is an ideal starting point that will give a good footing to jump into your first project based course such as Press Start.