To be honest, I don't really like this game very much, but maybe I'm just not a graphics guy. I'll try to give some suggestions:
1. Make the core gameplay loop more interactive. Currently there's just decorations and chairs that you can buy with money. Quests seem entirely unrelated to the main mechanic for the most part, and they're completely time gated which isn't great considering you can't speed up time. The chairs seem to be the only production boost, and they scale really harshly so for the most part the game doesn't really have any sense of progression. Maybe like, quests need a certain amount of money to complete and give you boosts? Another currency other than money that you can use to embark on quests to get new stuff would be neat.
2. Make the theme of "time" more relevant. It seems like a lot of the focus on this one is put on the supposed time that the customers are from, but they have no difference other than visual. Maybe they want some food which is specifically from the period they were in so you have to build a new kitchen which cooks that kind of food to satisfy them? Decoration could play into this satisfaction factor too, and this satisfaction could in turn boost the money they give.
3. A better visual indicator that there are workers automatically serving the guests. I was confused for a moment about why there weren't any new things after I bought the worker upgrades but it turns out they're just invisible.
Wish you some good luck expanding this. This has more potential as a long-term game thing than a short-term game.