どれは英語のイディオムあなたに難しいですか （私の日本語訂正してください）

私のかがく おれはかがくのだいがくいんせい。むずかしです、でもがんばります！

あなたのお気に入りえいごの歌は何ですか？ Maybe I should be embarrased, but my favourite Japanese song is Kyary pamyu pamyu's PONPONPON :3

タトウーについてあなたはどう思いますか？ I know most おんせん forbid them. But I've also heard that many Japanese people would be frightened of someone with tattoos. Is this true? What are your (Japanese people's) thoughts on tattoos? I have many large tattoos on my chest, shoulders, and arms. Will I need to hide them at all times when I visit Japan? :')

When to use ひらがな vs カタカナ I always thought that ひらがな was used to write Japanese words, and カタカナ is used to write 外来語. But in a message, a native Japanese speaker wrote "ゴメンね”. Using both hiragana and katakana in one word, and also using mainly katakana for a Japanese word (It was "sorry", right?) I'm confused what the rules for using hiragana and katakana are, can anyone explain it to me please?

文法明るい 私はノート買いました。ペンのいろ変わった。 緑色：名詞 赤色：どうし こん：てにをは、変化。 私は期待日本語の文法身につける。でも、私は日本語の文法難しいです身につけた！:') (私の日本語を訂正してください！）

これは間違っています何故ですか？ 私の文：「私の日本語正すください」 訂正：「私の日本語を訂正してください」 Also,「して」の意味は何ですか？ ありがとうございます！

ミスひんぱん何ですか？

人日本語学ぼうはミス頻繁で悔しい何ですか？

(What are some common mistakes, which learners of Japanese make, that annoy you?)

Also, 私の日本語を訂正してください！

A question for English learners, how do you learn swear words?

I was just thinking. Swear words are considered inappropriate to use in professional situations (like teaching), so many people learning the English language aren't taught how to use them.

But, they're important words to know if you want to speak fluently! As a native speaker I can tell you that, even though it's rude to say, "fuck" is one of the most expressive and versatile words in the language. It can be used for anything from humour to anger, or just general expressiveness. If you become good friends with native speakers, I guarantee you will hear swear words at some point (unless they're elders or devoutly religious), and if you're friends with teenagers you'll hear them all the time. Having only a partial understanding of how they work could lead to some unfortunate misunderstandings. 

So my question to English learners is, are you taught swear words? Do you think they're important to know? How do you learn about them?