Used to give a mixture from a bottle, drank well, then chewed and spit…

Used to give a mixture from a bottle, drank well, then chewed and spit out this bottle and so on until now, although he still sucks, why? The nipple is curved, but the bottle is ordinary, could it be because of that? And I also wanted to ask about nipples by age, definitely by age? My little one sucks 0-6 months, they don't take more than that, is it like that?