How to pronounce [n]:
Make the tip of your tongue touch against the upper alveolar ridge and let the airflow comes out from nasal cavity companied with the release of the closure in mouth and the vibration of the vocal cord. The sound of [n] is more like the “n” in English word “nine”.
How to pronounce [l]:
Open your mouth slightly, make the tip of your tongue contact the upper alveolar bridge soft and then let the airflow comes out from the sides of the tongue-tip with the vibration of vocal cord. The sound of [l] is similar to the “l” in English word “like”.