What is the purpose of my birth?
The higher purpose of your present life/birth is to either pay back or reap the rewards of the karmas of your past births. Life is 90% suffering and 10% bliss. the final aim of your human life/birth is to attain liberation from this endless and painful cycle of births/deaths/rebirths. This applies to everyone.
The lower purpose of your present life/birth can be known through your horoscope.