Je croispense que les entreprises qui ont créé les réseaux sociaux veulent volcherchent à capter notre attention.

Vocabulary: While "voler" (to steal) is grammatically correct, it sounds a bit informal here. In discussions about the "attention economy," the verb "capter" (to capture) is the standard professional term.
Nuance: Using "chercher à" (to seek to / to aim to) is more precise than "vouloir" (to want) when describing corporate strategies.

Quand j’étais à l'université, en 2012, j’utilisais Facebook pour m'abonner àajouter mes amies.

Terminology: On Facebook, you "ajouter" (add) friends. The verb "s'abonner" (to subscribe/follow) is typically used for Instagram, X, or public pages, rather than personal friendships in 2012.
Gender: In French, the masculine plural "amis" acts as the default for a mixed group. Using the feminine "amies" implies you are referring exclusively to female friends.

En 2015, je donn'utilisais Instagram et c’était la même chose : mes amies et moi avons postépostions des photos de nos vies.

Vocabulary: In French, you don't "give" (donner) a social network; you "utiliser" (use) it.
Tense Consistency: Since you are describing a repetitive action or a habit in the past, you should use the imperfect tense ("postions") instead of the passé composé.

Mais maintenant, je pense que les gens utilisent les réseaux sociaux d'une façon qui gaspillleur fait perdre leur temps.

Style: "Gaspille le temps" is a literal translation of "wasting time." In French, the idiomatic expression is "perdre son temps."

Ils regardent des vidéos de les e'étrangeres au lieu de secelles de leurs amies.

Contraction: "De les" is incorrect. When referring to indefinite people, use the contracted form "d'" before a vowel.
Possessive Adjectives: "Ses" refers to a single owner. Since the subject is "ils" (plural), you must use "leurs" (their).

C’est pour ça que je pensla raison pour laquelle j'envisage de quitter ces sitplateformes.

Register: "C'est la raison pour laquelle" is the formal equivalent of "C'est pour ça que" (That's why).
Nuance: Using the verb "envisager" (to contemplate/consider) sounds more deliberate and professional than "penser."
Vocabulary: In a modern context, social media services are more accurately described as "plateformes" (platforms) rather than just "sites."

Je crois que c’'il est plus important de passer du temps avec nos amies au lieu dequ'avec nos téléphones.

Grammar: You must insert the preposition "de" before the infinitive verb following an impersonal expression like "il est plus important."
Comparison: To compare two objects of your time (friends vs. phones), the "plus... que..." (more... than...) structure is more idiomatic than "au lieu de."