HI lucmru,
About "How to remove "New Outlook" from windows 10?" this request .
Uninstall the new Outlook - uninstall the app in Windows Settings: Open Windows Settings > Apps. Find Outlook (New) under installed apps and click the dots to the right of the name and choose Advanced options- then Uninstall. That will remove the app and the profile.
That should get you back in Mail (at least until they remove it) - if not, this article has the instructions to revert to Windows mail or Outlook for Windows: https://support.microsoft.com/office/toggling-out-of-the-new-outlook-for-windows-preview-ec102b39-5727-418e-ae1f-a1805434640c
The new Outlook is a work in progress - you can leave feedback and suggestions in the Feedback forum. Or, if a suggestion exists, vote for and comment on it. https://feedbackportal.microsoft.com/feedback/forum/89a8afa3-2e1c-ec11-b6e7-0022481f8472