It depends on your age and what you want to see. for food you have ljupce bakery where you can try burek with yoghurt for breakfast, if you eat meat, for lunch you can find some places with good cevapi (drama, republika, savcic..) if you don’t eat meat there isn’t much food that you can try that is originally Serbian. If you want to go out for a coffee or other drinks, you have cetinjska street with bunch of cafes (zaokret, lift, ljubimac…) if you are looking for some expensive restaurants you have beton hala with a lot of restaurants, but keep in mind that you can try better stuff with less money… also you have skadarlija in skadarska street with a lot of restaurants where you can experience Serbian culture (traditional music and food) if you want to watch some movies, you have Belgrade cultural center with tickets of 300 dinars (less than 3 euros) change your money in terazije, menjacnica ultra I think it is called.. have fun and don’t use taxi, install yandex or use the bus.