Airlines are required by law to inform you of your rights and the fact where you can file a complaint.
You are entitled to a compensation of € 125 - € 600, depending on the length of the flight and the amount of delay due to flight diversion.
You can ask for refunding your flight ticket if your delay exceeds five hours, but only if you decide not to travel.
You are entitled to financial compensation unless you have been informed 14 days before the departure of your flight or have been redirected to a departure date that is close to your original date, or unless the airline can prove that your flight have been cancelled due to exceptional circumstances.
Assistance by airlines
Depending on the circumstances, if you are denied boarding, your flight is cancelled or your flight is delayed, you are entitled to assistance (meals, communication and, if necessary, overnight accommodation).
In the event of denied boarding or flight cancellation, you may be offered the opportunity to continue your journey or get a refund.
Source: European Union (https://europa.eu)