OldGamer, that's not a hard task, what you need to do is:
1. Grab free sound editor, like Audacity
http://www.audacityteam.org/2. Open mp3 there and select section(you can do so with holding mouse and dragging it or clicking once and use arrows+shift for more precision) you want to delete on waveform.
3. Delete what you don't want and save file.
But I assumed you already extracted mp3, if not - there's plenty of on-line services for that, like this one
https://ytmp3.cc/ put link in, press "Convert" and save with
SMALL blue download button, be sure not to press on big black one, it's a trap.