I'm learning beginner in arabic and I can't find a proper grammar rule to figure it out.
There is a lot of lessons on long vowels but they are totally disjointed from the question "How to differenciate them from normal letters ?"
The perfect example to illustrate my question is "كيف نقول؟" The first time I read it on the front page of a book, I read "kif naqul ?". For me "كي" was the long vowel i. A native speaker corrected me by telling me it was "kayfa" but was not able to explain to me how to know without knowing the word.
For the same reason, why is it قو = qu and not قو = qewe because و is the waw letter.
Is there a grammar rule I can stick to, to recognize when it is a long vowel or a normal letter ? Or do I must just learn the word to know what is the pronunciation ?