课程的第一年被分为四个单元。

The first year of the course is divided into four ___units.

教科书的每个单元侧重于不同的语法点。

Each ___unit of the textbook focuses on a different grammar point.

所以，别担心，因为我会和朋友一起学习这个单元，他会教我任何我不懂的东西。

So, don't worry because I'll study the ___unit with my friend and he'll teach me anything I don't know.