I have 2 server using merge replication. One acts as a Publisher and one acts as a Subscriber. One day I want to switch the side, publisher become subscriber and subscriber become publisher. In my current way, I need to stop the replication, delete all publishing & subscription settings I was made and recreate it again. Is there any easier/faster way that I don't know ?
You can not "switch" a server's role in replication between subscribers and publisher.
Unless you are doing it repeatedly, I would highly recommend the method you describe, as it is the only supported method, and the most reliable.
It is possible to update system tables directly to change the name of a server, as I describe in this post. This method is unsupported, and is not easier--it simply shifts the type of work, depending on your priorities.
Note that in my post, I'm describing only the publisher, and only for transactional replication, not merge replication. You would need to identify different tables for merge replication, and do additional changes if changing the subscriber as well. However that article shows the general method. You would need to test heavily to ensure everything is working properly.