"Explain what you have already done."
Translation:Jelaskan apa yang sudah kamu lakukan.
You'll be understood if you say it like that.
Grammatically, it's not the correct word order.
In a sentence like this (passive type 2) nothing comes between the agent/actor and the verb.
Nothing comes between "kamu" and "lakukan".
Please have a look here for more info :
Passive type 1 and 2 , Tips & Notes, Addendum.