What is the best way to fix code in C# - sokoban?

Question

C++ / C#

Hello. What is the best way to fix the code? https://github.com/maksmkv/Sokoban . More interested in the code sections of the check that the stone hit the target:

if (map[x, y-1] == 'p')
                {
                    map[x, y] = 'g';
                    g.DrawImage(image6, x * 32, (y-1) * 32);
                    positionBall = positionBall + 1;
                    return true;
                }

If it's not difficult, tell me how to add a check if the stone was on the target, but then suddenly it was moved so that everything did not disappear. Few people did. THANK YOU