Some people get very good at Rap and improvised rhymes, but it's always been a challenge for me

Some were born with this talent to say words faster, the direct opposite of a stammerer.
From experience, you can be as good as your dad in smart-fast talking a.k.a Raping, by first, writing the words down, say it over and over again with some rhyme, almost every day, you'll be amazed what will come out of your tongues in two months.