I fixed the bug, where the inventory stayed during the cutscene! Sorry for that.
Also, what you were doing wrong was that you were pressing "tab" for using an item, which actually opens up the inventory. You were actually supposed to press "LMB" for the "Use" menu to open, and I had mentioned it in the controls as well as in the in-game tutorial.
Anyways, thanks for the feedback. I will surely update the game an add more puzzles & jumpscares. The game was made in just 2 weeks, and I even started 2 days late, so I didn't have enough time to add more puzzles & jumpscares, fix bugs..
So I hope you'll play the updated version when it's out!