Question

مطلب اونقدر سخته که از این ور می خونی از اون ور از یادت می ره.

Answer 1

I suggest to use the "no sooner ....than ..." form.

The subject is so difficut that no sooner I forget than I finish reading it.

یا به شکل دیگه :

....... that I forget all about it as soon as I finish reading it.