DERAILLEUR BROKEN
If the rear derailleur breaks off, shifting is out of the question. You will have to convert your bike into a single-speed bike. First remove the defective rear derailleur. Then shorten the chain. It should be tight around the chainrings and sprockets. Choose a gear with which you can still conquer the hills on the way home. Tip: Choose the middle chainring at the front and a sprocket from the centre at the rear, such as the sixth. If you live in a flat area, you can also choose a smaller one.