The correct answers are We are waiting for you at the bus stop. and I will see you at the concert tonight!

We use at for specific points or locations (like a bus stop or a door) and for events (like a concert or a party).

"In the door" is incorrect because a door is a specific point, so we use at the door.

"On the new restaurant" is incorrect because a restaurant is either a specific location (at) or an enclosed building (in), but never a surface (on).