There is an ID, but it’s on 4F (the ID has nothing to do with floors). So I’m guessing the first line either means “[someone] threw [something] away at a door on 5F” or “on the way to 5F” (which, looking at a map, is sufficiently non-helpful as a clue that it doesn’t matter if you interpret it wrong). It could also mean “someone on 5F threw [something] away”, which is very unhelpful.
The context for the more cryptic lines is that some of them tell you passwords, and others are apparently just graffiti.
だんこりろ は ちまりそ
Conclusion is it's bloody(My translator guessed on this one, and says it sounded unnatural)
.brev on ecnetnes ym ,oslA .noitcerid gnorw ecnetnes sihT :X
I want to die on a tatami mat
To “die on top of a tatami mat” (畳の上で死ぬ) is a phrase meaning that one dies a “proper”, dignified way. That is to say, not by accident or violence. Preferably, it’s of natural causes in one’s own home (and if you’re really lucky, in your sleep).
Of course, there is a sick joke here, too: the word “tatami” comes from the verb “tatamu”, meaning to “fold up”, among other things. And one of those other things is “kill”.
It's time to come back...
“This is the way back~”
Probably a blatant lie considering this game, but I’m not checking.