"Why do you want to do it?"
Translation:Proč to chceš dělat?
It is always good to start with the Tips and notes provided. You can also start with https://forum.duolingo.com/comment/31466920/Ordering-the-Czech-clitics-Introduction-2019-04-18 but this is a bit more advanced.
Certain words must be in the "second position" but please read the resources for more.