How to spend 4 days in Budapest with my Serbian partner?

Hi gorgeous people, My partner and I are visiting Hungary as it’s my best friends wedding. My boyfriend is Serbian, I am Hungarian (but I lived in a small town before moving abroad so I don’t actually know much about what to do around Budapest.) We are going in two weeks and staying a full week. I was hoping you could help us by suggesting what is actually worth exploring and doing! We’ll be there Tuesday-Friday. From what I’ve seen it’s going to be quite hot. We’ve visited together once before and saw Margaret island, Szimpla Kert, Halászbástya, done a boat tour and walked around some of the bigger malls. We’re both 27, big foodies, love technology, gaming and anything to do with dogs/cats. So far we thought we’d visit the zoo and have a spa day at Széchenyi thermal bath. I’d love to hear some suggestions on what to do/eat/explore if you could help us! Thank you ◡̈