Swap Qashqai for Audi A3?

Hello, I need your help with a (at the moment) tricky question! I have been driving a Qashqai Acenta 1.6 l for 3 years (i.e. year 2013) and would like to mention that I am totally satisfied with the car (yet!). My annual driving performance is about 8,000 km, definitely no more. Should it last 20 years???? With good care (necessary workshop visits)! However, I also think of the future, because I will probably not be able to find another new one anymore. The durability of the car should be (now’ laugh) already about 200,000 km. Now I consider whether I can change it for a used (about 8 years) old, Audi A3, diesel, with max. 120 hp and approx. 40,000 km change/exchange. I could still sell the Qashqai for approx. 13,000 – 14.500 euros. The car should be long-lasting and I wanted to drive it to the bitter end. And here I always read and hear that the diesel engines are unreliable?! Apart from Ka roserie and wear parts that occur everywhere. Or is there a more meaningful alternative to the Audi A3 and for my budget above? Bin Laie and wants to drive the car as long as possible. Maybe you have understanding for my consideration(s). Thank you for your efforts in advance.