wow. Thank you for the explanation. I did some research to understand what are you saying, because I am new in this and now I have thanks to you a much cleaner image, how it is supposed to work.
one more question: are the transactions picked up by chance from the mempool? Are there any criteria besides the econmic ones?
There used to be other criteria, but nowadays it 99,9% ecomic... The transactions with the highest fee per vbyte of transaction data usually end up in the next block. The biggest exepctions are transactions from pool operators, or people that payed pool operators to include their transactions into the next block