Choose a class among others on an element

Thank you for the reply! I did what you said and then clicked on on of the three classes, now are you saying that if I click on one of those classes like navbar then if I change anything in the properties blow will change for that class?!! I have to say clicking on any of the classes didn’t change any of the properties shown below it and the color of defined properties remains orange, so I don’t know what property is defined in which one of the classes !!!