Wash lemons and limes in hot water. Cut 4 lemons and 4 limes into slices. Squeeze the remaining lemons and limes. Leave everything with 1 l mineral water and brown sugar in a drink dispenser (approx. 5 l capacity) for approx. 1 hour. Wash the mint, shake dry and add to the lemonade. Pour 4 l of well-chilled mineral water on top. Add more mineral water little by little as desired.