Asalamunalaikum .I am 26years old female.I started praying and fasting at the age of 25 . I have missed 16years of prayers and fasts. I was not knowing importance of prayers nd fasts. I feel very sorry and have asked allah for forgiveness. my first question is (1)Why do i still have to make qada as i had no knowledge and my parents never told me anything .I asked for forgiveness allah is most forgiving will he still punish me if i dont make up for missed ones (2)why did allahs guidence came to me so late (3) Do i have to start making for missed prayers and fasts or can i do it after some years

Alhumdulillah you are blessed that He has guided you in this age and Alhumdulillah now you understand the importance of prayers and fasts.
Yes it was the duty of your parents to teach you in your childhood but after the age of maturity it was your duty to read and understand the rulings as you did now because you were born in shia family where you have seen the people they are praying and fasting it was enough to understand the importance of prayers and fasts.
1) you have seen the people that praying and fasting it was knowledge.
2) there was not any delay in coming of guidance . It was negligence.
3) yes you have to pay qadha inshallah you will be able to pay the qadha I suggest you simple way at the time of fajr pray prayer of the day and one qadha same with other prayers
When you are not busy or in week end try to pray qadha for two days
Inshallah you will feel peace and satisfaction and inshallah Allah will help you in this great cause . My sincere prayers are with you.