>>1312891Learn the "days to maturity" for crops you like to eat then look up your first frost date and how many days away that is.
https://www.plantmaps.com/interactive-netherlands-first-frost-date-map.phphttps://www.plantmaps.com/interactive-netherlands-plant-hardiness-zone-map-celsius.phpThen you will better know what stuff you may be able to grow before a killing frost and without a polytunnel or greenhouse. Where I live, which has a month or more less of a growing season left than yours does, we plant pumpkins, radish, cole crops, carrots, and a ton of other stuff.