Bike buying advice – for city riding and errands

Hi all! I have two Fuji bikes that I inherited from friends, and I love them each, but I’m considering selling one to get something that serves as a better middle ground between the two that I currently own.

I have one geared bike with a basket and wide tires that’s great as a daily commuter and for errands. The downside is that it’s heavy and tough to peddle uphills (could be user error with the gears tbh.) It feels slow and it’s hard to gain speed on this bike. (I’m a relatively novice biker fwiw.)

I also have a single speed Fuji that is super fast and light weight, an absolute delight to ride BUT the tires are so thin that I often catch flats on the slightest pothole or rock etc. it’s not great for city riding and the frame can’t take wider tires. I also can’t add any saddles or baskets to this so it’s not great for riding to work with all my stuff (laptop, lunch, change of outfit etc.)

I’m looking for something that’s an in between: fast, lightweight and can handle a saddle or basket. I don’t care if it’s geared or not. I’m thinking of spending around $500. Brands like breezer and retrospec look cool but I’m not sure what to look for.