1
I understand the lesson.
To express this, begin by signing 'I understand'—pointing to your chest and then flicking your index finger up near your forehead. Follow this with the sign for 'lesson' or 'class'. Be sure to nod your head affirmatively throughout the phrase to clearly confirm your comprehension to the instructor.
2
Now I understand what you mean.
Start your sentence with the sign for 'now' to establish the timing. Then, sign 'I understand' while showing a bright expression of sudden realization on your face. Finish the thought by signing 'your' and 'meaning', demonstrating that their explanation has finally made perfect sense to you.
3
I understand a little bit of ASL.
Begin with the phrase 'I understand', executing the index finger flick near your forehead. Next, sign 'a little' and then 'ASL'. Keep your movements relatively relaxed and use a modest facial expression to accurately convey that you have partial, but still growing, comprehension of the language.