I'm no expert but I wonder if unscrewing that hex bolt, then lifting the door up would work. With 2 people of course.

The six-sided slot is for a hex-head fitting. An Alan wrench or key is needed, and are commonly found at home improvement stores, etc. The picture on the left looks to be a special tool needed, so that one is probably best to avoid. Be sure to support the glass and put a folded towel over any metal or hard surfaces it might come into contact with. Tempered glass is tough, but when it breaks it does so in spectacular fashion into a thousand tiny pieces.

Use an non visible skrewdriver!

But seriously, this door is most likely installed like gate hinges. Loosen the top hinge, rotate, then lift door out.

I agree with just trying to lift it off.

Are you sure the gap doesn't appear by design? I've seen door hinges lift like this when they are meant to self-close.