kitchen gardening for the climate crisis

given the current direction of the climate crisis and the humanitarian catastrophe ongoing I intend to make my house and garden into as useful a place as possible for those in need. I have about 40 m² of garden to use, I read somewhere that this could feed about 2 people and that you need about 20 m² of garden to feed a person year-round. folks in my village suggested I start out growing pumpkins, carrots and onions together initially.

currently the garden of the social housing I live in is almost entirely tiled over. the municipality offers a subsidy of €4,- per m² of tiling replaced by greenery. my garden is 52 m² but I still need a little bit of space for walking and parking my bike so I should be left with about 40 m² of gardening space for which I should be able to get a subsidy of €160,- for the food garden.

could this amount be enough to get my food garden started? I live in the Netherlands where it rains a lot so I will likely be able to obtain most of the rainwater from my rooftop or a (for now) freshwater lake nearby. what do I need to learn about / read to build a reliable food garden?