The garbage disposal area is located behind the building. You can access it by opening the big gate, around the corner, with your (black) key chip. Please that the garbage bags need te be placed inside the containers.
If you want to donate good quality clothes or stuff, check the many second hand shops in the surroundings. Good quality clothes can also be put in special collection containers mostly located close to supermarkets or shopping malls.
If you want to donate your left-over food, you can bring it to Foodsharing Maastricht. A grassroots initiative that raises awareness of food waste and organises unconditional food redistribution.