It seems like it’s not just a VS related issue since you’re unable to open the .uproject file.
First, try deleting the Intermediate and Binaries folders and opening the .uproject file again. You might encounter the same message when you do so but don’t give up on the first try and try a few more times.
If the issue persists, verify the engine from Epic Launcher and once that’s done, try opening the .uproject file once again.
I’d also recommend using version control and having multiple backups of your project on a safe drive if you’re not already, to avoid losing progress in the future. Things might go wrong when you try to upgrade the engine version of your project, especially if you had certain plugins enabled in your project.