Praise be to Allah, and may Allah’s peace and blessings be upon the Messenger of Allah, his family and his companions.
As to what follows:
With regards to answering your question we say, success is by Allah Almighty.
If a person leaves Prayer intentionally then making qadha for leaving it will not help. It is obligatory to make taubah and increase in doing good deeds which include (nafil) prayers and being good.
As for what is mentioned that being consistent in performing obligatory prayers and their sunnahs will make you like a new born baby is not correct but you should strive in asking for forgiveness and increasing in making naafil prayers, perhaps Allah will forgive you.

Your brother,
Dr. Khalid al-Muslih
10 / 04 / 1425 AH