Okay, I did what you can see in the attachment. But I still can't make an example like in the previous post. I see that it is not very easy to do. I have found some examples but fail to implement them. Of course, if I succeed, I will post the solution here. I see that it is necessary to study well and understand the way of analyzing fft.

I thought some of the forum members knew the solution to my problem. Not everything can be achieved with a line of least resistance