Why lessons are limited???

Answer 1

Simple answer: Because they were intended to be for complete beginners, that's why! 8D

A little elaboration: When the teacher teaches her students that 2 + 2 is 4 those who are curious know that there must be more than 2 + 2 in that damn book 8P so they flip the pages and see additional examples on the next pages. By the same token, those learners who need more, search a bit more on Google for complete materials. 8D

Answer 2

You might want to elaborate on what you mean by "limited". Are you facing any issues with the lessons?