How do I switch from a merged branch to an new branch?

Use the following commands:

git stash: It will stash your uncommited changes.

git checkout develop: Go to develop branch

git pull: Get the latest code

git checkout -b "new branch" : Create a new branch

git stash apply : It will add your uncommited changes made in the step 1

if you wanna undo commits check this: How do I undo the most recent local commits in Git?

if you just want to change branch and create a new branch run this in terminal:

git checkout -b (write the name you want)

by running this you will create a new branch and also will switch to it.