When using the term before, you are referring to something that has most likely happened in the past, specifically prior to another event. For example, your 15th birthday would happen before your 16th birthday because your 15th birthday would come first. Another example would be when you think about how you get ready for your day. You would most likely get dressed before you leave your house in the morning.
When using the term now, you are referring to what is happening at this exact moment in time. For example, if I was driving at the moment then I would say, "I'm driving right now."If you were in math class and someone called you and asked what you were doing, you'd say, "I'm in math class now." Hope this helps!
