Here are the exercise sheets that I use with my students. I find that it takes 3 to 6 months for English-speaking adults to learn these sounds. You can share these with your own private tutor or you can work with the recording provided.
You can use these exercises as a warm-up or as a quiz:
1) as a warm-up exercises : listen to the correct pronunciation and repeat it
2) as a quiz : say the word BEFORE you hear the correct pronunciation. Did you say it correctly?