Before setting up a new theme, is it possible to save the existing one, in case I want to go back?

Hi, I am new to the site and new to wordpress. A few months ago, I paid for a wordpress website. I am note entirely satisfied with, so I want to try out the themes. Before doing that, I want to save everything I have, in case I have to go back to it, since I already pay for all that work. Hope you can help with it.