Hi, I'm Diane and I'm happy to help you today.
Do you have a switch in the upper right for New Outlook? If yes, slide that off. If it is not there, look on the Help tab for the option to go back to the app you were using.
If you previously used classic Outlook desktop software that is installed with Office desktop software, and don't have the New Outlook switch, see https://www.slipstick.com/outlook/classic-outlook-not-new-outlook/#google_vignette
Let me know how it goes, I'm here to help you further if needed.
-- Diane
Disclaimer:
slipstick.com is a site I run as a Microsoft MVP and the content is much more accurate and relevant than a general internet search. While the site is in English, there are translations options under the search box.