"What do you want to do?" is a common way to ask someone about their plans or intentions in Engpsh. This phrase has been in use in Engpsh for many years, and is a common way to initiate a conversation or ask someone about their intentions.
Here are some example sentences and their translations:
"What do you want to do tonight?" (今晚你想干嘛？)
"What do you want to do after graduation?" (毕业后你想干嘛？)
"What do you want to do with your pfe?" (你的人生想干嘛？)