I could explain it, but it wouldn’t really help you. Nevertheless, I’m including the relevant Wikipedia pages for your reference. If you really want to improve your pronunciation, then we need to know exactly how you’re pronouncing the sounds now, and then we could have you practice similar sounds, noting how they are different and what the have in common. This works best in my pronunciation lessons, where we can adjust the position of your tongue and other articulators, as well as your breath, voice, nasalization, etc. That allows us to make adjustments and get instant feedback. The L: https://en.wikipedia.org/wiki/Voiced_dental,_alveolar_and_postalveolar_lateral_approximants#Voiced_alveolar_lateral_approximant The N: https://en.wikipedia.org/wiki/Voiced_dental,_alveolar_and_postalveolar_nasals