"mais" as the word "but" is used in a negative way. "or" is not used everytime in a negative way, it's just a word to get two ideas together in the same sentence. For example : "Je suis sortie or il faisait froid" which means "I went out, however it was cold". "or" doesn't mean everytime "however" but on this case it does. I always says to my students it's better to learn a language without looking for a translation everytime, because a lot of things cannot be very well translated. I know it's not easy to do...

Pas facile d'expliquer cette nuance. Je dirais que "mais" est plus passe-partout tandis que "or" accentue l'idée d'opposition. C'est une conjonction qui s'utilise moins couramment et souvent dans un contexte de démonstration. C'est plus l'équivalent de "pourtant" que de "mais". Est-ce que ça t'éclaire un peu?

Merci beaucoup pour votre réponses.