The "Helping Children" and "Street Art" Achievements weresaid to have been fixed in 3.0.2 but appear to still be unobtainable on the GOG version. If you use GOG Galaxy, you can see that after obtaining every other achievement, the two remaining ones are said to have been earned by 0.0% of players.

Update: So I've been able to get 100% of the achievements on This War of Mine as of 2020-03-30. Occasionally the "Street Art" achievement will show up under the list of achievements which can be obtained, but then will disappear later. To be clear, the GOG version appears to have been fixed so that it no longer contains either the "Helping Children" or "Street Art" achievements, since neither can be obtained on the GOG release.