Dope = good, awesome
shit = stuff/thing
“Ass” in this sentence intensifies the phrase.
It doesn’t mean “butt” in this sentence.
If we put all these together:
“Some REALLY good stuff”
Although, the sentence you posted doesn’t really make sense (or atleast I can’t understand it well).
Also, please don’t use the word in formal sentences, because for one: they’re swear words, and two: they’re very informal (only use them with your close friends). :)