This is the 16293rd most frequent Turkish word.
yapmışsın
"You have done" or "you did."
The word 'yapmışsın' is used here to indicate that the subject has created or made a painting.
Ne kadar güzel bir resim yapmışsın!
What a beautiful painting you have made!
The word 'yapmışsın' in this context refers to the subject having made a mistake.
Böyle bir hatayı nasıl yapmışsın?
How could you make such a mistake?
In this sentence, 'yapmışsın' is used to express that the subject has completed or done a lot of work.