You can easily switch between different types of column layouts without worrying about losing your data. If you want to recover the content that is no longer visible on your website due to switching of column layouts, you just need to switch back to the previous layout and you will find all your content there.
To safely switch the content to a new layout just copy the content elements first from the current layout to the inbuilt clipboard and then change the layout. Afterwards, you can drag and drop the copied elements to the new layout from the clipboard.
Learn how to change the layout of your website.