I would like to buy a new phone

I have an iPhone 6s Plus. The battery is failing me. I can't have more than two hours of screen time without needing to charge it. It's also starting to glitch. When I try to open an app, it closes itself. I heard also that I can sell my iPhone for what it's value is.

I was wondering if Apple still sells iPhone 11because that's what I would buy.

Can I?