Hello ! I'm Aymeric, an independent advisor, and I'm here to help !
If you do an in-place upgrade of Windows 11, all your data and applications will be kept and transferred to Windows 11.
Connections to Office applications (or your Paint 3D files) will remain on your PC. The update does not delete any data.
Paint 3D will no longer be available after November 4, but even after that date, it will remain on your computer. It will just no longer be available for download.
Feel free to ask if you have any other question !