I think your acne looks like it's still quite mild but since you've just developed it you may want to find the best way to tackle it now before it becomes severe. You need to find the best line to use and stick to it as well as making sure what you eat will help to treat it inside out. I can suggest an able line that I've been using and it's worked wonders for me if you'd like

The red marks, or post acne marks, can last a few months  I think there are treatments that a derm could prescribe, but they do go away in time. I agree with Destinys1991, to tackle it now before it becomes more severe. I suggest a mild cleanser like Cetaphil or Cerave. Maybe the regime that is posted on this site would be a good place to start. 

The acne's quite mild. Maybe a 3-4?

It's difficult to tell how long the marks will take to fade. A couple of months is likely.