Want to add my two cents.
It can be hard to see progress when you compare it day to day. Think about weight loss, if you check the scale every day, you'll have low days, and high days. But, consistent work over a longer period of time, say, 6 months, you'll see how much progress has been made.
Think of it this way. Imagine you are in a very dark room or cave, where there is absolutely no light. If you light a single candle, you've increased the light by 100%. If you light a second candle, by 50%. 3rd candle is 25% and so on. With playing an instrument, that first candle is when you play your first note, you learn how to play the open E string. That's one candle. Then you learn more notes, or how to tune, etc. After a while, all those candles start to look the same, and you soon think you are not making any progress.
That said, sounds like your teacher is an ass. Yeah, an 11 year old can learn some new things faster than adults... like language. Kids that grow up in a multi-language household have no problem becoming bilingual because their brain is wired differently at a young age to learn language. As an adult, our brain is wired differently, and learning language is more of a challenge.
I'd shop around, find a teacher that you like and one that will encourage you, not make dump quips at your playing level.
But let me ask you this... do you like playing? Do you enjoy it? Don't worry about your progress or anything like that, just ask yourself, do you like playing the bass? My guess is yes, you do, otherwise you would have already quit. Remember why you are doing this, because you enjoy it and making music is a worthwhile pursuit.
Maybe take a break from lessons, and just jam along with your favorite tracks, or jam with some friends. I've found that playing with other (better) players has helped me become a better player.