I compiled a list of links that might be helpful if you don’t find your way around. Most of them I actually found on the Office Support Website, which you should check out as well.

Go to Microsoft 365 Login and Check these important links about Office 365.

ServiceURLs
Office 365 sign inhttps://login.microsoftonline.com
Office.com sign inhttps://office.com
Emailhttp://mail.office365.com
SharePoint team siteshttps://{domain}.sharepoint.com/
OneDrive for Businesshttps://{domain}.sharepoint.com/personal/{UserAlias}_{domain}/
Newsfeedhttps://{domain}-my.sharepoint.com
Public websitehttps://{domain}-public.sharepoint.com

Also, you should visit the Microsoft Office Community, which has lots of helpful topics about troubleshooting.