He must move

A cut piece from the wall can be separated using a knife. He must move inside so as not to damage the rest of the wallpaper.

Now you need to take a new piece and carefully grease it with glue. Next, it is required to attach it to the wall and gently roll it up with a clean roller. This is necessary to avoid new pollution of the edges of the piece. If necessary, they can be lubricated with glue, since over time they will be peeled off.