What should i say if someone said “what are you up to?”?

"what are you up to?" itu sama seperti "whats up" "what r u doing" Jadi jawabnya ya sesuatu yang sedang kamu lakukan saat itu juga.Semoga Membantu(:

You can say "nothing" if you don't want your intention to be known or to keep you out from trouble. (maybe)

But, you may explain your intention about what you are doing right now.

Hope it helps 🙂