Opel Agila Built 10/2000 1.0 12V consumed in the city about 8.5-9l!!!!

I bought the Agila 1.0 12V with 58hp Bj 2000 for my wife half a year ago because we were looking for an economical city flicker and now the nasty surprise! The Agila consumes an average of 8.5-9l on 100km that can’t be normal. It has only 3cylinders and is drinking as much as a 110hp car?!!! Lt. Opel is still normal!!!!! I just can’t imagine that even when I look past the fuel monitor it looks quite different there! Already new spark plugs ÖL+ have changed all filters but unfortunately without success! Furthermore clapping and or sometimes squeaks it grinds so funny loud from the engine compartment just when switching into the second gear or quite bad when the climate is sounding as if the V-belt was loose or somewhere a bearing would be broken which would squeak loudly. At Opel it was said it could be that a tensioning roller from the V-belt would be slashed about 200€ incl. installation cost one must But don’t you know why the Agila consumes so much or if it’s really normal?? And does anyone know these COMIC noises from the engine compartment?? Did anyone ever have that??? I know it’s bad to answer funny noises even though you didn’t hear them yourself or as soon as I can’t describe them correctly but there can always be someone who wants to answer them. The most important thing is the fuel consumption. Thanks