Each team has a corresponding SharePoint site. Changes made to files in SharePoint automatically sync to Teams (and vice versa), but if you want to make sure you have the very latest version of a file, you can manually sync the file libraries.
At the top of the Files tab, select Sync.
Likewise, you can select Sync in SharePoint to make sure you have any updates from Teams.
Sync updates from your cloud storage
Go to Files on the left side of Teams.
Select the cloud storage you want to sync.
Select Sync at the top of the page.
To learn more, see Sync SharePoint and Teams files with your computer.