First car: Used A5/S5 or A7?

Hello together, since I will soon move from the city to the surrounding area, in order to give me a little more rest and save rent, a car has to come. Audi has been my dream car since childhood and well, the companies already know how to do it with the rental cars – so I was convinced of the A5. Now, however, I ask myself which of the three mentioned it should be, and whether one should buy something like this as the first car? I would like to write that I also have the driver’s license. In general I would like to have an S5, it should be sporty, of course more expensive than an A5. But if you take an A5 with similar motorization, it looks quite similar again. An A7 would be right for me, but then one of the first generation for cost reasons. I took this into account mainly because I don’t like the Navi in the first generation, sonde rn rather that of the second generation, however, many used the virtual cockpit, which I don’t like. Perhaps another fundamental question: Would you take a diesel here on a work path of 16km or rather a petrol truck? I have already asked friends/relatives and they advise me on a diesel. But I am not quite convinced of it. I am grateful for your answers.