[Jenda_]

What total mileage do you have? In my experience, it will start skipping on some gears after 7000 or maybe 10000 km and then you need to change the entire drivetrain, because it got destroyer by the heavily worn-out chain.

Learning to fix the flat myself was good because I can do it immediately in 10 minutes without having to walk the bike to the shop (which are closed during evenings/weekends) and wait.