All over
あちこち (everywhere) I've been looking all over for you. Where have you been?
Amount to something
大した人物になる，成功する、ものになる If you work really hard, someday you will amount to something. Amount to something can also refer to an idea or plan's success. My plan really amounted to something. 実を結んだ
As far as (I'm) concerned
(私)にとって、私に関する限り As far as I'm concerned, JWUHS is the best girls' school in Kanto.
As far as the eye can see
見渡す限り At this school, there are trees as far as the eye can see.
Backfire
裏目に出る，逆効果 Your plan or idea makes things worse. My plan backfired! The result(s) is the opposite of what you intended.
(Be) better off
の方がいい If it rains on undoukai day, we're better off postponing (延期する) it.
Buddy, pal
お前、君、仲間 Both buddy & pal mean "friend", but people sometimes use these words instead of using someone's name. あまり親しくない人に対する呼びかけとして使われる。
Bump into
人と偶然会う、出くわす、遭遇する To meet someone (usually someone you know) by accident. I might bump into Kanako at Ultraman Shopping Street.
Change (one's) mind
気が変わる I was going to go to Hawaii this summer, but I changed my mind. I'm going to Okinawa instead.
Come on
ふざけないでよ！嘘だろう！やめろ！いい加減にしろ！ Come on, Mark! We can't memorize 6 pages of idioms! That's too many!
Come through
期待に応える Emika always comes through for her friends.
Come to mind
頭に浮かぶ What image comes to mind when I say the word, "blue?"
Crazy about
~夢中 Like something very much; be in love with e.g., Natsuki is crazy about BTS.
Come up with (an idea, plan)
(アイディア、計画)が浮かぶ，ひらめく，思いつく Who came up with the idea for your class's 応援発表のテーマ？