Students often work alongside their studies, commonly in restaurants (for example McDonalds, BurgerKing) or bars. You might want to look around your area to see if there are any cocktail bars, restaurants, or similar establishments where you could inquire about job opportunities. Alternatively, there are also beverage markets like "TrinkGut" where you could work as a cashier or stocking shelves.
Additionally, platforms like Stepstone and Indeed offer job listings specifically for "working students" that you can explore.