Muslims, if Allah is the all-knowing then what is the purpose of creatilng the disbelievers ?

I am a new muslim, so will answer your question to the best of my ability. Allah - God, creates life. When the infant is approxiamtely 3 months in the womb the angels come and blow life into it and preordainment of three things. One is life span, and this will not be altered by any life choices, another is if you will be lucky in life - of good/ bad character & I cant recite the third. Allah will know overall where you are destined, but how you get to heaven or hell is down to you and your life choices while in this world are down to your own mins. Allah provides your birthright as a muslim and the Quran as your guide and a lifetime to accept and repent if you have been awarded with bad character and the oppourunity & tools to change. Whether you accept that is down to you. You can alter your life with the help of Allah. He can change your destiny if he see's you are sincere in repenting or by guiding those he wills. You can change your life style but not your life span. Also in the night before Ramadan, the angels are back and forth between heaven and earth all night and muslims stay up and pray the whole night. It is revealed in this night Allah changes the destiny of one muslim and forgives all his past sins. So you see, Allah can change your destiny if you are sincere in wanting change to piousness in your heart.