Greetings, for some reason the menu with the tutorial did not work for you, I will explain to you here, the model of the key is highlighted in yellow, so you had to press the center of the LMB, then to open the door you need to press the right mouse button, you could see in the trailer of the game which door you need to open, door number 13, next to it the color blinks, this is still early access, there may be bugs here, thank you, let's try to fix it!