I agree. The correct translation should be: "What are you trying to do?" I'd suggest that perhaps the Greek sentence is also incomplete. I hope a native speaker can provide more clarity here. The other two versions offered by Rob43066 are also correct in English, but perhaps translated differently in Greek.
I am a little confused, because δοκιμάζετε looks like the word dokument, and a dokument does not try anything. I have been taught that consonants(?) in old words rarely changes, but that the vocals do. So, a word root here could be δκμζ/dkmt which is almost the same for both words. I rarely believe in coincidences.