Hi, I Have White Spots Over My Forehead Over A

hi, i have white spots over my forehead over a month now.
3 days ago i started Zarin cream twice a day.
may i know:
-how long does it takes to heal.
-how often should i apply the cream.
-am i allowed to put on any toner/moisturizer with the cream.
-how did i get white spots in the first place
-how to prevent it