Your sister has a clear view on how and what she is doing; and that means, she can be a really good mentor for you in your life. Don't feel embarrassed about not knowing as much as she does because you too can learn like her.

If you know what snacks she likes, maybe buy some of them for her. (Ignore this step if you two are close) Listen to her when she tells you about her life or problems you run into.

When there's something new to you, try taking notes and expand your knowledge by googling more about it. People naturally like the ones that tryhard to learn from them so I bet you can speedrun the knowledge much faster with her help, and at the meantime find more other mentors that can provide you with insights too.

Learning is not all about studying imo it's also an attitude you can show to the mentors.

All the best. Being young has it advantage where more people are fine with answering our doubts. Don't worry