"What does this cat eat?"
Translation:Kucing ini makan apa?
I'm used to saying "lagi apa?" to very casually say "What are you doing?" Or more formally "Anda sedang melakukan apa?"
I don't know how natural it would be to apply those to oneself "Aku sedang melakukan apa" but it's at least grammatically correct.
Also I don't think perbuatan works like that. It means "deed" or "action" and is a noun. You could probably say "perbuatan aku apa?" But it's unlikely to mean "What am I doing?" in the same sense as "lagi apa"