What could be the correct C# design pattern to use in following scenario?

I am working on creating a c# design for following requirement. I am creating this for a fitness website.

I have an article (as Text) and a exercise (as Image or Videos) as the base entity. Now i have workouts, middle entity, (A workout is basically a set of excercises or articles to be performed in a instructed manner, it will have 2 or more than 2 base entities to make the workout) above these two entities.

Next I have routines, top entity, ( A routine is basically two or more workouts taken at a time.) A routine can span for days, weeks, months or year(if provided).

Now i was thinking composite design pattern to implement in my application but not sure.

A little peek at database design to help with the c# design.

My database design would look similar to this one, check the image in answer.

Also a small example would help me.