Focus poor starting and fuel consumption

Those symptoms certainly sound concerning. Poor starting, increased fuel consumption, reduced power, and uneven idling can indeed point to fuel injection problems. Dirty or malfunctioning injection nozzles can disrupt the proper fuel atomization and delivery, leading to incomplete combustion and those symptoms. Given the mileage, it is plausible that deposits have built up over time. Have you tried using any fuel additives designed to clean fuel injectors? Has the check engine light illuminated?

I haven't tried any fuel additives yet; I was a little hesitant without knowing exactly what the problem was. The check engine light did come on a few days ago. Is there a straightforward way to check the injection nozzles myself, or would that require specialized equipment?

Given that the check engine light is illuminated, it would be best to have the error codes read by a professional. While there are methods for DIY injector cleaning, improper handling can damage the injectors or the fuel system. Considering the complexity of modern fuel injection systems, I highly recommend taking it to a qualified workshop for diagnosis and repair. They can perform tests to determine if the injection nozzles are indeed defective and advise on the best course of action. It may simply require a cleaning, but in some cases, replacement is necessary.

I took it to the workshop as suggested. They confirmed that the injection nozzle was defective, likely due to it being dirty. They recommended replacement. The total repair cost came to around 515€. After replacement, all the symptoms are gone! Thanks for your help in pointing me in the right direction!