Verify your files, you will be missing three of them and they will be auto replaced.
These three files are launcher files.
From your post are you starting from the Icons on you screen?
If yes and you are using steam start Steam from the start menu in the lower left, then go to the upside-down V in the lower right and select the Steam icon and start game from there.
This may or may not work but in the years, I have been on steam starting the games this way has never failed.
If it does work verify your files after each session.