To get started, you probably want to check out Razor Editing -
https://youtu.be/HEVKLiWkRkk
and Looping -
https://youtu.be/gbwq0jC8j-g and
https://youtu.be/oOBWvvSoXFk (and probably more Kenny and others' vids)
For your use case:
1 - Razor edit select your desired section.
2 - Copy and paste to new track at timeline.
3 - Un-select the pasted razor edit selection (by clicking somewhere else).
4 - Click on the newly pasted item to select (kind of goofy but a way to get out of razor edit - probably an easier way). Note - this new item is a copy of the entire item not just the selected area.
5 - Right click and choose Glue Items to now have just the selected area.
6 - Now you can drag out the item as long as you want and it will loop and changes made will be made to all looped areas.
It really isn't as cumbersome as it sounds.