Keyworks: VersionControl, TortoiseGit, Create branch

New Branch

Switch to new branch

Commit modifications to new branch
Push the new branch to remote

If the new branch is just used to concurrent development for yourself, the new branch should not be pushed to remote, because all users would get the branch if the new branch have pushed to remote.

Swtich to old branch

If you have created a branch in your local repository, then you should switch to your local branch(e.g. branch master), not remote branch(e.g. branch remote/origin/master), because the remote branch doesn't stash your modifications which haven't been pushed to remote.

Merge modifications from new branch to master branch