I have two branches branch1 and branch2 , how to combine two branches data together.
To combine the data you can place the logic from branch shape into a new sub-process and then use only single return documents shape to return the data from Branch twig 1 and twig 2 to the main process.
Agree with Srini. For an example of this see 4 (Good) Reasons to Use the Process Call Step.
Also, please try to use a more specific subject to your next post so other members have a clearer understanding of what you're asking. See How to Ask a Good Question.
Retrieving data ...