Free time activities:Vortrag korrigieren und ergänzen,bitte!

Ich muss in Englisch einen Vortrag über Freizeitaktivitäten von Jugendlichen halten. Die Aufgabe lautet: Reflaged on popular freetime activities of your age group. Include your own hobbies! Meine Gliederung dazu und das was ich bisher geschrieben habe, Structure:

1.What is a hobby?
2.What types of hobbies exist?
3.What are the most popular free time activities of my age group and why?
4.My own hobbies

1. A hobby defines as any activity a person performs regularly in their free time. Your hobby may not be as fascinating, watching television and surfing at the internet for new informations is also qualify as hobbies. Fortunately, no rules exist that say you can only have one hobby at a time, or that you have to keep the same hobbies throughout your life. In fact, you can try out new hobbies as often as you like and fall back on old hobbies anytime. The main goal of a hobby is to give yourself an break from your everyday work or school. A hobby is something you should do only for yourself.
2. Now, what hobbies exist in which age group?
People may have many different hobbies during their lifetimes. It is different from age group to age group. When you are a child, you played with dolls or toy trucks. When you get older, your first real hobbies develop. Some kids go out for a sport like football or basketball. Other childrens get more interested at a quietly activity like painting or reading. When you get older, mostly your hobbies have changed. You have a job and you haven´t so much freetime. So you search a free time activity, what you can do after work, f.e. jogging, swimming or you go to a gym. But there are also people who have not changed their hobbies, f.e. if you have collected stamps as a child, you`re doing it mostly even when you are 80. However, there are free time activities which are popular in every age group, f.e. watching TV, surf at the internet or meet friends.
3. What are the most popular free time activities of my age group and why?


Zu den 4. punkt kein Problem, aber zu Punkt drei fällt mir nichts wirklich ein. Ich kenn nat. beliebte Freizeitaktivitäten aber ich weiß nicht wie ich es formulieren soll mit den Warum. Könnt ihr mir bitte helfen und auch sagen ob das was ich bisher geschrieben habe stimmt?