Hello,
it seems that one of the required game files is missing or is corrupted. Please verify the integrity of the game cache to restore and repair the game files:

1. Open Steam client.
2. From the Library, right-click on the game and select "Properties" from the menu.
3. Select the Local files tab, then click the "Verify integrity of game cache..." button.
4. Steam will verify the game's files and restore them if necessary.