Dear Chloé_Van_Steenkiste, "landover=trees" in an unusual tag, we would usually either map individual trees or call it "landuse=forest" (or "natural=wood" if unmanaged). Also, you did not set a changeset comment when uploading; it is considered good practice to write a few words about the change you are uploading. See https://wiki.openstreetmap.org/wiki/Good_changeset_comments
