What warranted the price change from 2.39€ to 9.99€ in a game that hasn't been updated in years?

After the tutorial, the first mission is impossible. There are too many documents to gather in a larger size area, I can't outrun creatures, I don't have enough ammo to fight them all, I take major storm damage inside a building, and I don't gather enough stuff to do much other than die. I can't gather more than 3 documents before I eventually get killed. Part of the problem for me is that by the time a creature sees me and runs at me, I take damage by the time I aim at them and shoot....

Is there only a single, "Single Missions"? or do you have to beat a set number of waves to unlock more missions? I can only select the snow mission. Do you have to finish all the campaign missions or something? I'm only about 2/3 of the way through campaign - stuck on that mission where you have to defeat the one monster......

Как вы думаете, чего не хватает в игре? Что лучше добавить, а что убрать?