Like (how it is used in the example sentence) is a stopgap to avoid saying er..., IOW a word inserted to keep the flow of the sentence going. There is no direct or indirect translation. It is not even slang, just an ugly habit. I know a guy who keeps inserting "wie schon gesagt" for the same reason, but that is not a general translation. Filler words exist in German too, though.
Sis is just short for sister (more or less the female equivalent of bro) and in that capacity not really a slang word either. Or did you mean one of the more obscure meanings?
Lowkey, if used as adverb, is indeed slang, more or less meaning nicht wirklich (not really), or kind of. I don't know a direct slang equivalent in German. Of course you can say: "Ich bin irgendwie halbtot" (or even "Ich bin iwie halbtot").