okay it was fun and pretty decent for your first game. tbh i would give a solid 6.5/10 here are some suggestions:
1. the menu is very important and i recommend making the buttons clickable and recommend a settings tab.
2. In the menu background instead of something like a monster it would look better if it was the buildings photo outside of the building.
3. the graphics are pretty decent but you can improve it definitely.
4. the npcs felt really unhuman they always say the same thing everytime some characters should scare us by teling creepy things about the building etc.
5. Soundtracks and the optimization was really good
6. there are some small bugs for example i got locked in the apartment of the woman since the door closed
7. running and stamina really would add the game more depth
8. The font of most texts other than the texts in the building looked really poor i recommend a pixel style font.
9. the game was a little too short it would be perfect if it was like 20 minutes
10. there was some lighting bugs i didnt really notice but the unreal engine was constantly telling that there was a lighting error.
11. there must be a story and more depth to the game.
12. you can add jumpscares espacially in some apartments when we open the door for example in this game.
13. the npcs almost all of them had the same model its reallly hard to make a model but it makes the game feel bad.
14. the main content of the game which is fixing the gasses should have had more impact on the story and maybe a minigame to fix the gasses.
15. The game lacks visual feedbacks and it should be more polished.
16. The thumbnail was nice and had creepy feel to it.
17. You should take inspiration from other indie horror games
That's pretty much all nobody should complain since the game is free and the idea of the game was pretty nice and it was definitely somewhat scary.