Support for Microsoft 365 app (Word, Excel, Teams, etc) and other Microsoft products is available from Microsoft in a variety of formats, most of it free.
1. Microsoft 365 Help & Learning: https://support.microsoft.com/en-us/microsoft-365
A great place to get started. The "Get Started" page for each app provides a series of tutorials in both video and written (with screenshots). For Excel, Microsoft has also partnered with TakeLessons to offer affordable private lessons, online group classes, and a curated collection of videos from experts .
Get started with: Word | Excel | Powerpoint | OneDrive | Teams | Sharepoint | Outlook | More
2. Microsoft 365 Training: https://support.microsoft.com/en-us/training
Video training for all Microsoft 365 apps. Most of the video resources are the same ones available from support.microsoft.com
3. Microsoft Learn: https://learn.microsoft.com/en-us/
A more formalized, advanced learning resources aimed at professionals seeking certification. Learn is a great starting place for those seeking to learn more advanced Microsoft products including Azure, the Power Platform (Automate, BI, etc), and the .NET framework. Learn also has learning resources related to Teams, and the Educator Center, which offers lessons, professional development, and even certifications for using Microsoft in education.