Although motherhood doesn't come naturally to some people, they can still be a good mum. It means being honest about when you are struggling, asking for help,educating yourself. The fact you are asking these questions make me think that you will be a great mum, because you clearly care.
Your whole life changes when you become a parent - in my experience it didn't take long to adapt to motherhood, it happened naturally, your body is incredible, so many changes happen beneath the surfaces that help you to bond with your baby. Like many mothers, I became hyper aware of my baby's needs, (it just happened, I didn't do anything special).
Hormones have a huge role,. If you win the hormone lottery everything is easier, if you get PND it can be a real struggle. In those first few months you need to take each day as it comes. Don't be afraid to reach out for support and please remember you are not your mother.
My mother neglected my siblings and me. I think I am a good mum - I certainly enjoy being a mum and my baby seems happy too. I was lucky, I adapted quickly to motherhood but I know that's not everyone's experience. If you find it hard at first it doesn't make you a bad mum, in fact it can make you an even better mum.
It's a marathon not a race. You learn as you go. Just enjoy your baby, as you find your rhythm you will grow in confidence. There are good days and bad days. Just be prepared to throw out all the ideas you had about how you will be in motherhood. Every baby is different and needs to be parented differently. You will quickly learn what works for you and your baby, what gets them to sleep, what comforts them, what makes them happy. You will know the face they pull before a big poop and you will know if they seem a little off for whatever reason - that's the instinct thing. You spend all your time with them so these things become obvious. Instinct is strong
Fyi, my mother has borderline personality disorder which may be why she didn't take too well to parenthood. I think for most people it is quite natural to bond with your baby and understand their needs. I agree that it is very instinctual and intended by nature.