hello, did someone already installed a macos Big Sur or Monterey on a mac book pro mid-2012 ? If yes did it work or did you experienced problems ? Thanks for your feedback

A mid 2012 MacBook Pro cannot be upgraded to Bigs Sur, Monterey or later. Catalina is the highest possible. Also see the following from Identify your MacBook Pro model - Apple Support

MacBook Pro (Retina, 15-inch, Mid 2012)

Model Identifier: MacBookPro10,1

Newest compatible operating system: macOS Catalina

Tech Specs: MacBook Pro (Retina, 15-inch, Mid 2012)

User Guide: MacBook Pro (Retina, 15-inch, Mid 2012)

MacBook Pro (15-inch, Mid 2012)

Model Identifier: MacBookPro9,1

Part Numbers: MD103xx/A, MD104xx/A

Newest compatible operating system: macOS Catalina

Tech Specs: MacBook Pro (15-inch, Mid 2012)

User Guide: MacBook Pro (15-inch, Mid 2012)

MacBook Pro (13-inch, Mid 2012)

Model Identifier: MacBookPro9,2

Part Numbers: MD101xx/A, MD102xx/A

Newest compatible operating system: macOS Catalina

Tech Specs: MacBook Pro (13-inch, Mid 2012)

User Guide: MacBook Pro (13-inch, Mid 2012)