Hi, Ji-young! ♡♡

I think all kinds of languages are difficult to study. ✔

But English is not too difficult to learn because we can have many opportunities to learn. ✔​

English is an international language so we can easily access.  ✔​

It's up to our time and effort. ✔

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1. I rolled up my sleeves. -> I turned up my sleeves. 

=> Your sentence has a correct grammatical structure, but this has the correct usage/ expression.

2. I'm sure it'll turn up. ✔​

3. Please turn down the volume.​  ✔