Here are a bunch of links that will probably help the most:
https://zcusa.951200.xyz/en-us/microsoftteams/enduser-training
https://zcusa.951200.xyz/en-us/microsoftteams/training-microsoft-teams-landing-page
Also, MVPs are a useful bunch. Here's a filtered list for current Office Apps MVPs:
https://mvp.microsoft.com/en-us/MvpSearch?ex=Office+Apps+%26+Services&sc=e
And many ex-MVPs (still just as clever, but maybe have more time to offer)
https://mvp.microsoft.com/en-us/MVPReconnectSearch?kw=teams&sc=f
All the best,
Pete