Summarize the following:
Write down words and say them out loud to yourself. You can buy a workbook if you want some extra help, or find worksheets online. You can find plenty of videos online that offer the correct pronunciation of words. Try to match what you're saying with the correct pronunciation. It doesn't matter if you know what the word means if no one else can understand what you're saying. If you don't have a Bengali friend to speak with, you can always find one online! Search "Speak with a Bengali" online and you'll find plenty of sites that allow you to speak with someone over the Internet. Even if you're just exchanging small pleasantries this is a good start. Find a movie that is entirely in the Bengali language. Even if you don't know what is going on this will help you get an idea of the rhythm of the language and how words are said. You'll be surprised how helpful it is.
Practice on your own. Practice with a Bengali online. Watch movies.