Breaking the sentence down

Can anyone explain how did 興味のある事だと理解するのが難しいレッスンかもしれません ended up being translated as “If you are interested you will try harder to understand.”?

Interesting exists (in the) thing, therefore understanding のが hard lessons “can’t be known” (the future can’t be known, but it is possible that it’ll happen this way)

“If the thing is interesting, it may be possible to understand hard lessons.” - this is my translation and as you see it has a complete different meaning than the original translation. So… What am I missing?

You skipped some words.

“If you are interested you will try harder to understand.”
興味 の ある 事 だ と 、あなた は 一生懸命 に 理解 しよう と 努める でしょう 。

“The lessons are difficult to understand.”
理解 する の が 難しい レッスン かも しれ ませ ん 。

LOL. I’ve combined two sentences in one and haven’t even noticed. :))
ありがとうございました。