Native speakers drop sounds and blend words. That is why a sentence you can read still sounds too fast in a real conversation. Reductions are the missing piece.
What English reductions are
A reduction is a shortened, blended form: going to becomes gonna, want to becomes wanna, got to becomes gotta. The words are still there. The mouth just does less work. If you only studied the full forms, you will miss the reduced ones when someone talks at full speed.
Why they make you sound more natural
Using a few reductions in casual speech is not sloppy. It is how American English actually moves. Save the full forms for careful speech. Use the reduced forms when you are talking with a coworker or a friend. Word stress still has to land. For that side of the work, see fixing word stress mistakes.
How to practice reductions
Pick one pair. Say the full phrase, then the reduced one. Then put the reduced form in a sentence you would actually say. Listen back. Daily work like these pronunciation tips is enough to start.
If you want guided practice on reductions and the rest of American English, start a free trial at pronunciationpro.com/trial/.