Hi Mildred, I have changed my theme several times. As John mentioned below make sure you back up your content before making any major changes.

Best wishes,
Michael

Hi Mildred - just make sure you back up anything you have already created before you switch themes 😎

Wordpress compliant themes will not change the contents of your site. All plugins remain configured as they were before. Sometimes, you will need to reset the colors and theme specific settings as they are not always transferable to the new theme.
Allan

Changing your theme is unlikely to cause any problems. Any plugins you have installed should continue to work as before