「難しい」は、difficult、hardといいます。「先週のレッスン」はThe last week's lessonです。もしあまりにも難しかったときは、The last week's lesson was too difficult for me. 「先週のレッスンは難しすぎた」というように、too「あまりにも～すぎ」をプラスするといいですね。
レッスンをもう少し簡単にしてほしいとリクエストしてもいいかもしれないですね。＾＾
The last week's lesson was difficult for me. Could you make it a little easier next time?
→先週のレッスンは難しかったです。次はもう少し簡単にしていただけないでしょうか？
I was quite challenged by last week's lesson, teacher
I felt really pushed during the last lesson, teacher
You were doing the first, second and the third conditional during the previous lesson. It was just a review lesson, but when the conditionals were all mixed together, you found yourself wondering if you really did understand how to use them.
"I was quite challenged by last week's lesson, teacher."
"Don't worry. It was difficult material and you actually did quite well!"
あなたは、一番目、二番目そして三番目の条件文を前回のレッスンでやりました。
今回は、ただの復習レッスンですが、全ての条件文をごちゃまぜにしています。
あなたは本当に自分がこれらの使い方を理解しているのか不安になってきます。
"I was quite challenged by last week's lesson, teacher."
（先週のレッスンは難しかったです、先生）
"Don't worry. It was difficult material and you actually did quite well!"
（大丈夫ですよ。難しい教材でしたが、あなたは良く出来てましたよ）
I thought last week's lesson was challenging/difficult
I struggled with last week's lesson
Last week's lesson was difficult/challenging
When you want to explain that a lesson you had in the previous week was difficult or challenging, then you can say it in the following ways:
-I thought last week's lesson was challenging/difficult
-I struggled with last week's lesson
-Last week's lesson was difficult/challenging
先週のレッスンが難しかったと説明したいなら、次のように言うことが出来ます。
【例文】
-I thought last week's lesson was challenging/difficult
（先週のレッスンは難しいと思いました）
-I struggled with last week's lesson
（先週のレッスンは難しかったです）
-Last week's lesson was difficult/challenging
（先週のレッスンは難しかったです）
The three sentences you see provided above are terrific ways to express to your listener that last week's lesson was difficult. In the third sentence you will notice the phrase go over someone's head. If something goes over our head that means it was very difficult to understand or grasp. This is a phrase that is common in our everyday conversation and it would make a great addition to your vocabulary.
上記三つの例は、先週のレッスンが難しかったことを伝える素晴らしい言い方です。
三つ目の例には「go over someone's head」が使われています。「go over someone's head」は、理解するのがすごく難しかったことを表します。日常会話でよく使われるフレーズですので、語彙に加えておくといいと思います。
If you found something difficult you could also use the word 'hard'
So you could either say 'I found last weeks lesson difficult' or 'i found last weeks lesson hard' that would tell the teacher that you would like an easier lesson
難しい（difficult）ことは、'hard'という言葉で表すこともできます。
ですから、
'I found last weeks lesson difficult'（先週のレッスンが難しかった）
又は
'I found last weeks lesson hard'（先週のレッスンが難しかった）
と言えます。これで、先生にもっと易しいレッスンがいいということが伝わると思います。
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