#and immediately there's a deppen leer zeichen on the front page

[clouds-of-wings]

Because there seems to be so much confusion in the notes by people who speak some German but aren't fluent, the correct way to phrase this would have been: "Meine scheiß Katze Gniesbert ist schon wieder in meinen Gaming-PC geklettert." (Since it's a meme, the errors in the sentence of course contribute to the humor.)

Replacing the ß with an ss: it's normal in Swiss German, where the ß doesn't exist. Also, Germans often either get it wrong (even though the rules for ß usage are much more logical now than they used to be before the 1990s) or neglect to use it, especially on phone keyboards where the ß can be hard to access.

"Scheiß" indeed comes from "Scheiße" (shit) but can be used colloquially as a non-declinable adjective. It's a fairly recent development. It's der scheiß Hund, die scheiß Katze, die scheiß Menschen. It literally means "shit dog" etc. and can be insulting, but in terms of what it actually means in this meme, "fucking dog" etc. is more accurate. The stress is on the substantive. This is actually such an intricate matter, because you can also say Scheißhund, Scheißkatze (the Duden knows only this version as of yet), then the stress would be on the first syllable and it would mean "very bad dog/cat" or a dog/cat that shits a lot. Some discussion on the matter here.

Also: "sie ist in meinen PC geklettert" = she has climbed into my PC "sie ist in meinem PC geklettert" = she has climbed up/around inside my PC

The hyphen between Gaming and PC is necessary, don't let anyone tell you differently. "Gaming PC" is using a Deppenleerzeichen which will make you look stupid to, well, me and other grammar... enthusiasts, aka the only people whose judgement matters ;)

pic of my pc