In this clip you can see how much Robertson being in an offside position affected Donnarumma.
i feel like this is something that has been discussed before, possibly last season, but anyway;
Is Roberston offside when he's pushing? If you cant be offside from a corner, when is he offside? As soon as someone from his team touches it (in which case the pushing has ended as is 'foul' or 'not foul') or from some strange interim period when the ball is in the air?