If you have already played regular Metro, and then decided to play the Enhanced Edition (or vice versa), then cumulative achievements for kills will not work. Make 50 kills with a car; spend 500 units of resources on crafting/cleaning weapons - you will receive these achievements during the game immediately, and the rest you will not receive at all.

1. Go to the Steam library and right-click on the game, disable synchronization with Steam Cloud in the settings.
2. Find the Metro Exodus folder and delete it, it is located here: your drive/users/your name/saved games
Check it out, it should work.