This is story related so it can't be missed. Here's just a little tip for second part of the quest where you need to fetch two deer livers. There are two mission markers on the map in Soviet installation which are placed on deer spawn points. However only one deer spawned in my run. So I traveled to Siberia wilderness and killed a deer there. It did count and completed the quest stage.
So - if you can't find deer in Soviet installation, just look elsewhere (valley is also a good place)