Game is pretty well done, but I had found some bugs. Also I can propose some improvements.
First of all, stationary phone is calling while lights are off - wtf? Also not to mention that sometimes you can't give a cup of coffee to people, they just don't take it.
As I understand, difficulty levels are different by rate of events such as phone calls, lights went off and asks for coffee. It would be grate if you have less time to bring a coffee/answer a phone call on harder level. Also stamina can be reduced on harder levels. Difficulty also should increase while you are playing (idk if it's already imported) and your stamina should increase too because of trainings you get at work xD. You should pay more attention to some small things, creating a storyline, that would make your games better. Even if development of this game is finished, you can implement these things in your future projects.
Good luck with your projects.
Stay safe and don't get sick.