the best part of

the best part of:  绝大部分；某物的大部分；最精彩的东西
The best part of what I've learned from Andrew's course is that I can easily model upon his effective approaches to practice speaking American English as fluently as expected. 
从阎老师的课上学到最宝贵的东西是，我很容易模仿他那高效的方法来练习说流利的美语，这完全是意料之中的。
As a matter of fact, I am quite aware that teaching English to people of all age groups is really the best part of the job, which is really something！  事实上，我很清楚教各个年龄段的人英语是令人欣慰的事情,而且这种感觉非常棒！ 
That's really something:  真了不起；那真是了不起；那真了不起