The Grammar

1. I think the grammar easy for learning is 進行形. We may only learn this grammar's form ( be + Verb + ing ) and 1 meaning ( procession ) . The variation of verb " be " and how to make question sentence are same with verb " be " , so we can understand it soon .

I also think the grammar difficult for learning is 一般動詞 . First of all , we can't understand the defference between this grammar and verb " be " easily . In the case that the subject is 三人称単数 , we must put " s " or " es " on the verb . In that case , we also must use "Does " in place of " Do " when we make question sentence or negative sentence but we can't understand 三人称単数 , as much .

2. I think the grammar easy for teaching is 受身形 . This grammar is similar to 進行形 . We only teach this grammar's form ( be + perfect participle ) and only 1 meaning ( passive voice ) but it will be hard for students to memorize perfect participle words .

I also think the grammar difficult for learning is also 一般動詞 . I do part-time-job in cram school as English teacher , there are many students who confuse verb " be " with 一般動詞 and can't understand 三人称単数 . I have no idea how to teach it .