Have you tried verifying the game cache?https://support.steampowered.com/kb_article.php?ref=2037-QEUH-3335Verify integrity of game cache
From the Library section, right-click on the game and select Properties from the menu.
Select the Local files tab and click the Verify integrity of game cache... button.
Steam will verify the game's files - this process may take several minutes.
Once the process is completed, the Check Window will automatically exit.