Buying a car – acting?

Hello, I am currently looking for a small cheap smarti that should last only one to two years, so the budget is also limited to 25 – 2700 euros. But that’s not the point, I was already at different dealers and I noticed different things. It was all small dealers, so not big companies but those at all corners of Berlin. Point 1. The general action. After a test drive it always came to the usual. Nothing! I’m no one who’s brazen and the car was free, but there was a case, for example, there was a smart for 2690 € looking ugly from the outside, but the rest was right. He was on summer tires. The dealer said the price is the last one, even without winter tires etc. Many cars still stand on summer tires I have the feeling that is partly intentional because now the winter is coming. And I have experienced that now with every dealer that he didn’t want to go down. Is that really so that they have no more room for manoeuvre? Point 2. On the internet there is a price for a car for 2700 € , I drive to find the car on the square and see it for 3300 €. Then I say that on the Internet there is another price, then comes, – Yes the price on the Internet is without guarantee. May a dealer without guarantee be able to pay Do I always have a guarantee from the dealer? Point 3. Tüv- There are many dealers there is then TÜV and AU new. Does this mean that the vehicle is completely re-made at its expense. So if the Tüv says brakes have to be made that the brakes are taken over by it? Thanks already for your opinions.