1. I read many mangas when I was young. (Although I don't think I get old)
-> 1. I read many comic books when I was young. Although, I don't think I got older.
マサイさんの答えです(というか今回はマサイさんしか答えてくれなかったんです)ここはいくつかの点を説明します。
ア. manga って言葉は日本製のコミックという意味で普通に使っています。たしかに comic book の方がよく通じるけれど。
イ. manga を英語に使うときも s を取らない言葉です。(たまに s を使う人もいるけど)
ウ. 後者は惜しいけど、Although, I don't think I've got old/older の方が自然かと思います。
2. My friend started to write English blog.
-> 2. My friend started writing English blogs.
自然な英語ですけど、blog を複数形にする必要がありません。
My friend has started to write an English blog.
って方がいいと思います。
3. Amazon shipped out my book yesterday. I was looking foward to get it.
-> 3. Amazon shipped my book yesterday which I had been looking for.
語順がちょっとぎこちないです。which の前にコンマが必要です。
3. Amazon shipped my book, which I had been looking for, yesterday.
4. If it isn't rainy, I will be on a bike ride again.
-> If it isn't rainy, I will go bike riding again.
これはいいです。I will go for a bike ride もいいです。
5. I've been sick since this Wednesday and now getting recovered.
-> 5. I've been sick since this Wednesday and now, I'm getting recovered.
語順がちょっとおかしいです。
I've been sick since this Wednesday, but I'm getting better now.
I've been sick since this Wednesday, but I'm recovering now.
あたりがいいと思います。
6. I found many Naruto' fans include overseas.
-> 6. I found many Naruto fans including in overseas.
意味がちょっとずれていると思います。
I found that Naruto fans include many overseas.
I found that there are many Naruto fans overseas.
という意味だと思います。
7. Meet me darling on a seaside balcony.
-> 7. Meet me darling, on a seaside balcony.
いい線行っているけどコンマが一つたりません。
7. Meet me, darling, on a seaside balcony.
ポイントは me darling です。方言かスラングか知りませんけど、me が my の代わりに使うことが多いですよ。つまり、me darling = my darling という解釈があります。
それを避けるためにコンマを使います。