Something too much gets into the tank

Hello.

At present I need approx. 18-20 liter fuel (driving 30% city 20%, Bundesstr. 50%, highway).
At all events, this seems a little too much to me. I'm not driving a 20-litre car!?

With the exception of the following slight crashes, the car, engine, etc. this at now almost 270TKM.

-Lamda probe is gone, is made at next customer service
- Occasional slight variations in speed and oil pressure

What could the fuel consumption now be too high, only on the barrel?

A 2 weeks ago, I had these values: (almost all electric eaters on)
City 15-18 liters
Bundesstr. up to 12 litres
Motorway 13-14 liters up to 160

If leaky petrol lines are considered, where should I look best?

Many greetings