You have two ways to resolve this problem
Use Merge, but it creates an extra commit for merge
Alternatively, you can do a rebase.
Let’s see how this can be done:
Checkout each branch:
git checkout b1
git merge origin/master
git push origin b1
With rebase use the following commands:
git rebase origin/master
Thus, you can update your git branch from the master. Here is an excellent tutorial for git please go through this link and you will get your basics of git more clear.