看看这句对不对

我想你大概是想说; 我得努力学习我的薄弱科目。I need to study harder at subjects which I'm weak in.
你的那个yo，我想大概是to。study是及物动词不需要介词。再说你用study，这个harder用在哪里都感到不好读，我觉得用work hard at（致力于）也就是“努力学习”，实际上在英语里说“努力学习，90%的是用work at.“得” 我觉得应该是“不得不”的意思，所以我觉得应该这么说。
I have to work harder at the subjects which I'm weak in.

I need to study harder on the subjects what I am weak in.

错了本人不负责……

I need you to study harder on the subjects which I'm weak in.

大概就是这样

是表达"我学得不好的课目希望你得努力学好它"吗?
I hope you study harder on the subjects which I'm weak in.

I need to spend more time on the subjects which I am weak in.