Speak more slowly. Get the pronunciation right - and I mean absolutely perfect and natural - and then speed up later. If you're trying to race your words, you're much more likely to babble out a heap of nonsense which makes sense to no-one. For that matter, record yourself and see if what you are saying does make any sense.

Lyrics of rap music will not be the best teacher of English. Typically they are not grammatically correct, nor would they make much sense for every day use. I've heard that watching movies with the subtitles on will help, as well as actually speaking to someone in English on a daily basis.