Challenge 9 - Quick sort

[AbsoluteBeginner]

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Unfortunately, a box remains in the upper left corner when the first larger block is moved
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Maybe someone can find the error?

(translated by Google translator)

Hi all.

Scout,
Your program works without errors on my computer.

Besides, your program has given me back my interest in life. After the shelling of my city by an intercontinental ballistic missile, which the whole world is now talking about, I felt very bad. 
But your program has given me my life energy back.

Now I will continue to create a program for my improved sorting method.

Thank you, my friends, for being you.