If I understand correctly, you're interested in changing the texture of your natural hair so that it's more amenable to growing long. Unfortunately, there's no medical option for changing the texture of the hair. Occasionally, texture changes do occur as a side effect of chemotherapy drugs, but we're certainly not going to prescribe those for cosmetic reasons! This is a case for a well-trained hair stylist, not a doctor, but anecdotally I will say that you may find that a chemical hair relaxer does the trick. Good luck to you.
If your hair situation is hard to explain it may be best to see a doctor for an examination for possible options.
We ae born with a hair character that stays with us throughout life. There are various cosmetic products that can change this as you use it daily. See a hair stylist.