How to bring together different branches of development?

Question

git

There is a script that is actively developed.
We make our own modifications to it.
Every time a developer rolls out a new version of the product, we manually compare, add what doesn’t work from ours, and combine it all.
How can this be simplified? Didn't work with git. How to competently make such mergers? Which way to start reading / digging?

Answer 1

Basics of branching and merging , I hope this helps you.