UML/Design Pattern: Need help to check my UML for its correctness

the task is:

Photo of the task

I'm new to UML, so I tried hard and I have these answers (look below). How could I improve them? Where do I have mistakes and what should I edit?

Question 1:

Answer1

Question 2a:

Answer2a

Question 2b:

Answer2b

For the third question I'm confused and I don't know how to draw that. Could you give me suggestions?

P.S. For any questions - ask in comments. I will try to answer asap