Bitcoin is not a proof of stake so it can't be staked. The exchanges that asks you to do that are putting your Bitcoins into their custody and loan them to the other users which sound it make easy to believe that you're staking because you get percentage of returns of what they have promised their users to have. But, Bitcoin is proof of work and you don't get to stake that. That's why if you ever put your bitcoins on exchanges for futures, spot or staking, you're doing it wrongly so just HODL them.