Sorry to have let this slip by. The insect in the image (very clear, thank you!), is the nymph (juvenile, immature, "baby") stage of some kind of leaf-footed bug in the family Coreidae, as near as I can tell. However, I am not familiar with that many European insects; and nymph stages are almost impossible to ID anyway. I can say that it is a plant-feeder, sucking sap, but unless there are overwhelming numbers of these, they should not be considered pests. Thanks again for your patience.