How can I save food and wood up600k?

The resources will be produced in the farms, lumber yards and added to your warehouses. If you have a lot of troops though then you will not be able to produce a lot before it starts to be consumed.

You will however also earn resources in reward boxes from hourly events, clash or provinces, etc. These are stored and can be used to top up your warehouse levels when needed. Only use them when you need them though.