The time to complete a divorce can vary significantly. The theoretical fastest is three months, but the reality is usually significantly longer. 
Divorce always involves financial and emotional issues, some of which can be challenging. If you have children, it will involve parenting issues. Complexity adds time, and the biggest complexity for most people is the emotions. I have worked with couples who have taken years to and other couples who have taken months to divorce. It very much depends on your particular situation, and especially each person’s emotions and readiness to work through the issues.