I only get about nine kilometers per every litre.

When was the last service / tune-up?

Check for stored fault codes. Check the O2 sensor. When they get old, they respond slower, which will affect fuel economy.

Standard or automatic?

Take it to a repair shop for service. Stick with one service shop so that they become familiar with your vehicle.

Dealing with someone in person is better than trying to diagnose over the internet.

Thomas