Im going to say that they used the structures to store
heat.
and of course to cook food on.
Well, the first problem there is that it doesn't seem to have been a living area. They didn't find a lot of charcoal, which would have been abundant if they were using it for heating and cooking. They didn't find a lot of kitchen waste, which is abundant in the campsites of primitive humans, both modern and Neanderthal.
Also the circles are rather large for fire pits. 6.7 meters (22 feet) would require huge amounts of fuel.
And then, why would they need heat that deep in a cave. Caves are noted for maintaining a constant temperature. Neanderthals did wear clothing and if it was a little cool they could just put on another layer.
They are also rather deep in the cave. They are "about a third of a kilometer" (1000 feet) into the cave. Primitive cave dwellers didn't typically live deep in caves. They lived near the entrances so that they could get in and out. A thousand feet is a long way to carry the groceries in the dark. They of course didn't have electric lights to light the way.
And of course all of your other suggestions are really off the wall.
Bill Gill
