Your teen doesn’t really “think you are stupid” until you “start talking and confirm it.” You have been a teen and you imagine you know what they are going through. Try to keep in mind that you have never lived their life. No matter how much similarity there is between what they’re going through and what you went through, their experience is new and unique and as soon as you start talking about what you went through, there’s bound to be some minor difference that will convince them that you don’t know what on earth you’re talking about. That’s the point at which they stop listening altogether. When they want your opinion (and they do), they’ll ask for it.