How can I adjust canvas/project to work in this way?

I would like to work a project like in the gif (with this kind of “rotoscoping” idk(?)), how can I put a background image that doesn’t lose quality where I can work on top of it (I’m not asking to import some image and work in layers, I’m just asking if the way the gif is I can do it). /

you can import image as reference layer: layer → new → new reference layer from file
just note that reference layer can’t be transformed, it will adapt to dimensions of your sprite.