1. マリリンさん、どこでくつをかいましたか。
２．マリリンさん どんなくつをかいましたか。
You missed は after マリリンさん. Note that it works as a question directly asked
to Marilyn if は is not there.
あおいくつ
をかいました。
Page42 練習２
See the example more carefully.
この教科書は絵が多いです。（わかります）
--> この教科書は絵が
多くて、わかりやすいです。
You also need to change the i-adjective in the first sentence into the -te form, as you did in the last one 苦くて.
Page43
The most common Japanese translation of motorcycle is オートバイ or バイク.
Page44 練習６
1)
You gave another question to the question.
Q: もっと大きいサイズはありませんか。
Do you have a larger size one?
A: すみません。大きいサイズはありませんか。
I'm sorry. Do you have a large size one?
You need to see the example more carefully also here.
例） （新山口駅／止まる 徳山駅／止まらない）
--> 新山口駅には止まりますが、徳山駅には止まりません。
The given hint of the answer is
（Mサイズ／ある Lサイズ／ない）.
So, what is the correct answer?
2)
You need to think about the situation where the conversation is used. The reason すみません is used in #1 is that the conversation is done in a shop and the answerer is a salesclerk. There is no reason to say "I'm sorry" in the answer even if the answerer is a hospital staff.
Page 45
Again and again, you need to see the example more carefully.
Q: この本を読みましたか。
A: ええ、読みましたが、あまりおもしろくなかったです。
Notice that この本を is no longer mentioned in the answer since it's obvious. Your answers such like 英語を話しますが or 運転免許を持っていますが are not wrong, but sound too repetitive and therefore odd.
And finally, you asked us to check too many exercises at one time. It's better to ask it one by one. My two cents.
