PrestaShop 1.6.x. How to switch themes without changing modules settings

1. In your PrestaShop admin panel go to Preferences > Themes section: 
2. Click on Advanced Settings next to your active theme: 
3. Find the Directory option and select default-bootstrap:
   
4. Click Save button to confirm the action and refresh your website. You will see the default theme.

Hopefully, this tutorial was helpful for you.