Tercüme - Türkçe-İngilizce - Herseyi bir anda unutsam ailemi, gecmisimi,...

Hi Lenab,,

I'd say:
" If I suddenly had to forget everything..."

That would make a perfect "if clause"

Yes, I agree, but "umutsam" is conditional. Isn't "should" the word to use then??

Well the conditional form is : If + past + conditional

That means that the conditional forms you used in the second part (I would never forget ..../ I would never change...) calls a past form for the first part.
Therefore:

" If I suddenly had to forget everything (...) I would never forget ....."

OK! Then I change it!