Find a teacher who has knowledge of phonetics to help you. A good teacher should be able to help you in two steps: 1. First, to learn how to hear English sound distinctions that don't exist in your native language. If you can't hear them, you won't be able to pronounce them. But if you can't hear them, you also won't know which sounds to learn unless you have a teacher who can guide you and identify the difficult sounds. 2. Next you have to learn to say them. You can't simply listen and repeat, because your brain will think all sounds are the same as sounds already in your native language. Instead, you need a teacher who can tell you how to position your mouth and tongue to make the sounds correctly; and can listen to you and give you feedback. Good luck!

How can I improve my English pronunciation? Find good examples of English which you can follow, and ask for feedback often. Yes, this means talking to other speakers of English, especially advanced and native speakers.