How to show Sharepoint site expanded view by default in teams?

Hi Planet_Maine, dear Will,

I cannot understand, what you mean about 3 columns in a teams website (?). It would be great if you can upload one or 2 screenshots on what you now have and then intend to change in the linked SharePoint Website...

Building an MS Teams-team means, that you also have alreade a SharePoint Site in the background. A Team in MS Teams is basically another SharePoint Site, but with more collaborational power then a basic modern SharePoint Site.... This Site has as default a SharePoint Library and in your MS Teams team it is a Tab called "Files"- Each Site has also got pages, which show certain webparts, and each page has a default layout such as 2 or 3 webparts. Do you mean that? -

I assume you have changed the default page, called "Start". This is only ONE of many pages you can create on your own. Or you have this default "Documents " library, and this contains of columns, thus...

To view all your pages you can always click on the link "site content", than go to the App called "Site Pages Library". Each page is like an online paper, only to show different libraries or lists in your Site. Sites are NOT the same as pages in SharePoint, pages are like walls in a house and in each wall you have webparts like windows. 

A bit complex, I guess you are new to SharePoint basics, isn´t it? To grab these essential stuff you need to learn these differences between, pages, library files and lists in SharePoint. Then you can easily change, what SharePoint Page is your own user-defined creation in MS Teams then. Pls. explore this site to get more basics on SharePoint, for free: https://connor.collab365.community/creating-sharepoint-sites-lists/ 

Hope that helps you in your first steps, greets, Eva.