Purchase advice Leon III ST FR

A few basic questions about tips and simple opinions. For us, only one annual car can be priced. The following came from the rental company Avis. Leon III ST FR Facelift EZ 05/2017 22000 km 2.0 l TDI 150 hp manual gearbox Lots of equipment, 8 packages, e.g.: full LED, rear-view camera, PDC v+h, GSR, lane holdassi, Navi, sound system, seat heating etc. Stands on all-year tires, has “only” a set of rims. from the Avis fleet test drive was good. Brakes top. I was not aware that you have to put many things like driving profile and ears on parking or something about Carmenu. Except for a few, and I mean two, scratches on the trunk flap inside plastic covering ( 😀 ) and a small scratch on the top of the painted loading edge was nothing. No stone blow, no condensation in headlights, no parking scratcher, no indoor scraper or dirt, no visible water stains on the inside of the door, interior or so, no scratches on the rims. Price was already at <19,500 € incl. approval. This is quite good for NRW as far as I know. Is the warranty extension (for 1 year 300 €, 2 years 1000 € and 3 years almost 2000 €) worth? If so, how long? What should be paid attention to technically what I also recognize as a loan? What are negotiation tips? Thank you!