翻译：1.听懂老师说的英语是很容易的。2.我们应该避免与同学吵架。

it is very easy to understand what the teacher have said.(宾语从句用陈述语气）

we should avoid quarreling with classmate.
avoid doing

1、it's easy to understand what the teacher says in English.

2.we should try our best to avoid quarrel with others.

1. understands English which teacher said is very easy.
2. we should avoid with schoolmate quarrelling.