Learn Arabic (Modern Standard): من وجهة نظري، يجب أن نمنع السيارات في وسط المدينة. - From my point of view, we must ban cars in the city centre.

This is an Arabic possessive chain (Idaafah). The phrase is made of وجهة (point/direction) and نظر (view/sight). In an Idaafah, a possessive pronoun suffix like ـي (my) can only be attached to the very last noun in the chain. So it literally translates to 'point of my view.'

In the phrase يجب أن نمنع (we must ban), what is the actual subject of the verb يجب?

The verb يجب literally means 'it is necessary.' The grammatical subject is actually the entire clause that follows it: أن نمنع (that we ban). Because the subject is a clause (which is treated as a default masculine concept), يجب stays in the third-person masculine singular form, regardless of who is doing the action.

If we were reading with full vowel endings, what vowel goes at the end of the verb نمنع?

It takes a fatha (نمنعَ, namnaʿa). This is because it directly follows the particle أن (that), which forces the following present tense verb into the subjunctive mood (mansub).

Since السيارات (the cars) is the direct object of the verb, does it take a fatha for its case ending?

Surprisingly, no! It takes a kasra (السياراتِ, as-sayyārāti). السيارات is a regular feminine plural noun (ending in ـات). In Arabic grammar, regular feminine plurals are a special exception: they take a kasra in both the genitive case (like after a preposition) and the accusative case (when they are the direct object).