Thanks a lot for your comprehensive feedback which is much more than "your two-cents", haha.
I edited the GUI a little bit. It was of course not sorted yet since I was not sure if I am going really to implement it, but I guess so.
About the HP, the number is just secondary. The bloodbag would lower it's volume when the girls gets hit.
Increasing the number size would look weird. I do not want to let the GUI be in the focus though. Any suggestions?
On the game-wise side, I was thinking about much more freedom: The player can decide which of these GUI-Parts should be displayed and also which GUI-Parts should only display if they reach a certain value (dangerous-mark).
The ammo had infinite bullets due the idea of the loop. She would camp there while the animation repeats and repeats. However I changed it now (the number is still to be edited), to represent the threat of survival she is in. Thanks for this hint! Infinite sounds pretty "overpowered" and "boring" - specially in a survival.
I am missing the the thirsty GUI but I do not know how to display being thirsty. First thought: A plant in a pot.
The idea is funny but when I looked at it, it was more like "meh". Maybe I have to reorganize on this. I tried using the cut-view into the plants inner being and filling this with water.
But this feels not good and is not really expressing the need of water.
Making the plant dry feels maybe too unique in comparison to the other GUI-parts and too hard to predictable.
Also the brain is containing the sleep-meter, too. I guess this is okay.
There are also plenty of other ideas for the upper part of the GUI. Plasters, painkillers, ... all kind of usable items.

As for the monster: I edited it. Made it bigger and scarier. More blood, more bones, and better shading.
At the moment I am also working on its appearance. I got a little animated example for this.
First there is nothing. Just the girl heard something from the rather silent night.
Then something attacks the door. The door gets strongly damaged and then, after another attack, a monstrous blade (made out of bone?) shines through.
The light turns off. I might add a lamp, working and then stopping to work. I need to change the window-light-management, if I want to go for this idea.
Maybe removing the right window or letting it be nailed with planks?
The light returns, maybe rather powered by a short lightning than the lamp itself.
From this lightning the monster can be seen and it will start to try to attack the girl.

This is just a rough "sketch" animation to visualize the main idea. The first frame, when the door starts to break, is way too fast, of course.
I mentioned the rest already, though (concerning lighting).
Thanks for reading! I would really like to hear your thoughts or to see your edits (if needed to visualize your ideas)!