Hi again @jaki01. This time was a bit difficult but I think I found the solution. The idea behind this position is to try to enclose the black king by his own pieces:
1. ... Rb4 2. cxb4 + 3. Ka6
If white promotes a Queen or Rook then the position is a draw.
If white promotes a Knight: 3. ... b8 = N + 4. Kb5 Kc3 5. a5 bxa5 6. Kxa5 draw
If white promotes a Bishop: 3. ... b8 = B 4. Kb5 Bd3 5. a5 bxa5 6. Kxa5 draw