Sometimes the choice between de and du, de la, des is simply a question of whether you're describing a noun or indicating a possessor.
French has four different possessive constructions, which can seem daunting until you realize that English does too - you've probably just never thought about them before.
To emphasize to whom something belongs, you can use the possessive à in one of three constructions.
In English, we use 's (apostrophe s) to indicate that one noun possesses another. The French equivalent is the preposition de, with the order of the nouns reversed.
French possessive adjectives (mon, ma, mes, ton, ta ...) are used in front of nouns to indicate to whom or to what those nouns belong. They're more complicated than English possessive adjectives because there are different forms depending on gender and number.
French possessive pronouns (le mien, la tienne, les siens ...) are used in place of nouns to indicate to whom or to what those nouns belong.