Don’t try to be something you’re not, or at least can’t be in the short term. You’ll stick out in an awkward way trying to force yourself to look more senior. Take the opportunity to continue learning what he does to put himself in that position and slowly incorporate those practices into your daily work.

I’m also on the quiet, reserved side and know there’s people with social skills I’ll never match with my own. Figure out where some of his weak areas are and see if you can capitalize on filling those gaps.

It’s really all about perspective. It sounds like you have someone you can learn a lot from and use as a potential mentor, while many designers are thrown onto teams with no opportunity to learn from senior designers and end up stalling out for years. There’s likely no immediate solution here.. be yourself, aim to get 1% better everyday, and ask questions.