Reliability of a ForFour??? Petrol or diesel?

Hello, wanted to ask the following question, I wanted to buy a Smart ForFour to start a trip to Europe. That’s why I need an extremely reliable car. I wanted to ask Deshlab how reliable the Smart Forfour is. Which is more reliable? Petrol or diesel? I have heard that the timing belt has to be changed at 70,000 km, which costs more than 1000 EUR. Is that true? Which bigger things are still available at a Smart Forfour? Because I want a Smart Forfour. ufen, who has about 60-70,000 km. Would be happy about your experiences. Thank you Greetings