Why do i have the food production lower than the troups consumption?

Food production is limited by the level of your farms plus the bonus of any stationed heros or research. If you keep training troops though their consumption level will keep going up.

The good news is that it won't actually run out of food as the consumption stops when supplies are low. The bad news is you can't save up a lot if food as the consumption starts again as soon as you reach a certain level. You need to earn and save up food resource items from challenge reward chests.