It's correct. Only we write "vas" with capital letter as a sign of respect ("...molim Vas..."). If you want to use "još", you can say: "Molim Vas još samo trenutak, nismo odlučili" (That you could say if someone has already asked you before and now again, but you're asking for some more time.) or "Molim Vas samo trenutak, još nismo odlučili" or "... nismo još odlučili" or "...nismo odlučili još" :) Actually in this case you can put it at any of those places and none of them sounds weird. As you see "još" is more than welcome at any place in this sentence ;) Croatian is pretty flexible with placing words sometimes.