Manchester United have finally signed their key play, it's good that they've strength their attack to avoid the goal drought of last season, Mbeumo is an experienced premier league player and would really improve Manchester United's attack, but they don't have to settle for only Cunha and Mbeumo they'll need a midfielder, goalkeeper and a striker then a right wingback if possible.
With Bryan Mbeumo's entry into the Manchester United team, it will help improve the right side of the Manchester United attack. besides his experience, he was quite fast and productive last season, making him the right player for Manchester United right now. but as you said, he can't work alone, Manchester United needs a midfielder and a striker to make Man United's performance even stronger. as for the goalkeeper, it seems Onana will still be Man United's goalkeeper and they have no intention of looking for another goalkeeper.