As VIP you can change challenge without losing the what you've gained so far!
As VIP you can activate up to 5 challenges at the time, normal users can only activate 2!
A challenge is one to several tasks that you can choose to activate. You can have two active challenges at a time, if you deactivate one you lose what you have achieved so far, so remember to complete it before you change. However, VIP members can have up to five active challenges at a time, and they do not lose what has been achieved so far, so they can change as often as they like. There will be new challenges every Tuesday at 10.00.