Why is it so important to pronounce English correctly?
One of my students at a language school where I teach asked me why teachers repeatedly urged students to work on their pronunciation. She said that she and other students were always going to have an accent, so why was it so important?
The answer is a simple one. It's not about losing the accent, it's about being understood. An accent is OK, as long as it doesn't detract from understanding. Unless you learn to pronounce English words correctly, and practice doing so, you run a high risk of...not being understood, even though you may be using the correct word.
So, work on pronunciation, it makes all the difference.