White should move the white knight. It adds protection to the rook. Next, threaten the queen (F3-E1) with the knight so you have pressure on the queen. Queen is forced to move and at best can only take the white pawn on a2. Then white clearly has a winning position! (next move would be pawn takes black knight (F5-G6)
Cheers.
RE: Chess problem 35 / Schachaufgabe 35