Ok... before I start, let me tell you this ... If u are dealing with Arabs, we never really care about the nunation ( ٌ/ٍ /ً = un/en/an) or the tashkeel (ُ /َ /ِ = u/a/e) but for exams' sake/reading Arabic literature/ studyinh Quran, you have to know this:
Unlike english, Arabic has 2 types of sentences: nominal/verbal
Nominal= subject (noun/pronoun)+predicate ▪Example: الوردة جميلة (Al warda jameela)
Though it's translated in English to "the flower is beautiful", it has only 2 Arabic words
For such sentence, we add ( ُ ) to the subject (if noun) =الوردةُ (Al wardto)
Yet, to indicate that the nominal sentence is over, u usually add nunation to the predicate = الوردةُ جميلةٌ ( Al wardato jameelaton)
So in this example: انت أستاذ أردنى
The nominal sentence is أنت + أستاذ And أردني => adjective (صفة)
So it'll be أنتَ أستاذٌ أردنىٌّ Anta ustathun ordoniun
•As for pronouns, they have rules but I won't include them to keep it simple
Verbal sentence = verb+subject+object or verb+object + subject
For such sentence, we add ( َ ) to the object and ( ُ ) to the subject.
Example: شرب الولد اللبن => شَرِبَ الولدُ اللبنَ Shareba alwalado al-labana
Hope this makes it clear and helps you.