The yellow arch things on the roof are to prevent birds from nesting up there and from flying into the HVAC system. Don't ask me how I know this. (Actually I'm just making that up, but I tend to speak with authority having worked my way through college and grad school, and a bit after, in one of those McCareers).
For next time perhaps, there is a third alternative in TS3 for food service to consider that I use a lot. That would be the bakery store set displays with the NRaas Cupcake mod so that the displays carry whatever kinds of food/recipes you want to make available to your customers. It's won't be exactly a fast food joint as you won't see the workers preparing the food or working/cleaning a fry station, but it does do a pretty good job of emulating counter service. I find that the bakery cash registers still make a mess of Role Sim assignment even with NRaas Register in play, so instead I station one or more custom Role Sims by way of Arsil's mod from MTS behind the counter so it looks like they are actually working back there. Others' experiences may vary, but we all still have "billions and billions served" or whatever. :)