Learn Italian: Provo a capire questo trucco magico. - I try to understand this magic trick.

In Italian, certain verbs require a specific preposition before an infinitive verb. Provare (to try) is one of those verbs, and it always requires a. So, to try to do something is always provare a plus the infinitive.

Could I use cerco di instead of provo a here?

Yes, you could say cerco di capire. Both provare a and cercare di mean to try to do an action. Notice that cercare requires the preposition di before an infinitive, while provare requires a.

Why does magico come after trucco?

In Italian, descriptive adjectives usually go right after the noun they describe. Since magico (magic) describes the noun trucco (trick), it follows it.

Does questo change if the noun is feminine or plural?

Yes! Questo (this) is a demonstrative adjective, which means it must match the gender and number of the noun it points to. Because trucco is masculine and singular, we use questo. If the noun were plural, like tricks, it would change to questi trucchi.