Sidewalks: What are they for?

I live in a town with narrow sidewalks.
The sidewalks are uneven. Tree roots and earthquakes have made them dangerous to navigate.
But this space is shared with pedestrians, skateboarders and cyclists.
Yesterday I heard a girl call behind me. “ON YOUR RIGHT!”
I had no idea what that meant, but when I looked round, her mother was shouting, “ON YOUR LEFT!”
I called out to them to explain what these instructions meant. Apparently this is sidewalk cycling etiquette. That’s cool, but how does that shouting work for someone who has a hearing impairment. I don’t have a hearing impairment, but I’m mindful of those who do.
Today, I walked to and from the store.
A pre-teen lass trundled towards me on her skateboard. She wore a helmet and other protection.
She was skillful and stable, but I chose to step aside and let her pass.
But this young lass was aggressive and flipped her skateboard at me, back and front.
The expression on her face was aggressive, but it wasn’t a crime.
A few years ago, a dear friend was knocked over by a reckless skateboarder on the sidewalk and she suffered a shattered hip.
I must be getting old and shoogly.