At this point, the safe is the most unclear to me.. after trying for almost two hours now to find the combination. The gauge puzzle doesn't seem hard, it's just the finesse that can be a little difficult to achieve.
Viewing post in New puzzles
We will make this more clear in our next update, as many didnt seem to find the connection there.
In the shelf with the books there is a picture on the wall which shows different medical items of different height. You must adjust the books with the right topic on that height and then put the symbols in order of the items on the picture from top to down at the safe.