That's what I figured - that you weren't able to access the menu. So the object in the lower left is just the inventory, right? Have you tried doing what I suggested and moving your mouse cursor to the top or bottom of the screen? Just to say you did, you could always try the F keys... like F1 or something. I assume there was no brief tutorial??
Did you get the game from Steam? Or GOG? I would suggest posting your question in the forums there for an answer.
In my PC corner for the winter, gaming, knitting and reading.