Watch your favorite English language TV show or movie, and as the characters speak, repeat loudly the exact words they are saying the moment you hear them. In other words, 'shadow' their dialogue in real-time. Don't worry about getting every word or sound right - focus on listening carefully, moving along quickly and keeping pace. After the movie ends, repeat the exact same movie and do it again. And again.
By forcing yourself to speak at native speed, your brain becomes hyper-receptive to what you are hearing, and you will find yourself not only picking up the words quicker and quicker, but also unconsciously mimicking the inflections and vocal nuances that are usually difficult to learn for a non-native. It will also fix the stammer that comes with uncertainty or lack of confidence. In this way, the actors in the movie become your speaking partners.