About what you asked me in my post, I leave you this link, which is the closest I've seen to a bicycle shop here in Havana. They don't sell things.
It's a workshop and bike rental. They offer mechanics courses as well. They have an Instagram account.
https://peakd.com/hive-177745/@dahpilot/new-way-to-discover-havana
On the subject of changing the chain... mmmm, yes. Fortunately I don't have to change the one on my new bike. A friend of mine measured it and he says it's not worn enough to change it yet.
Today I finished cleaning the bike.
Before and After
Hooooooooooah! Nothing like a cleaned drive-train. I see you going around the island on that bike soon.
😁