Close button is not working and need to insert new function

[gasereldib]

Hello, I noticed when I push the close button, it doesn't work and I tried to track it but I failed.

I'm a beginner so the code level is kind of advanced and I want to make a function contains a loop for making some classes for the range of the frequency like a classifier. So is there any hint for making this? Or where could I use it?

Thank you