How long will it take to get divorced?

There is no way to answer that, there are too many factors. First I note that you are in Sydney Australia from another post. ANY question on law needs to include your general locale as laws vary by area.

Do you both agree to the divorce?
Does Australia have no fault divorce?
Is there going to be an issue about the division of assets.
In another you post you indicated there was at least one child involved, will there be a custody problem?
How backed up is your local divorce court?

All these among others will bear on how long the process takes.