What does five past mean in french

Explain what has to happen when you use être instead of avoir for the formation of the passé composé? il an english explanation with steps if possible

Is this french sentence grammatically correct? "vous aimez dessiner, prendre des photos, jouer aux jeux vidéos et les animaux. alors, je pense qu’un jeu vidéo designer ou un informatician sont des bons métiers pour toi." should des be changed to de?

When you take french in high school, would you already have to have learned french or no?