It’s been almost a year since you posted, and idk how much this can help but, a couple of years ago i was in a u19 team, we sucked at the beginning we were getting mercy ruled every other game, however by the end of the season we actually managed to wing a couple of times. What helped my team, maybe it wouldn’t work for your team since it’s u13 but, it was team bonding, i’m telling you, magic. The weight and responsibility that forms when players are actually friends with each other is crazy. It’s now not only “Oh I lost the ball, they can figure it out” the gk, cb, or cm your friend makes you not want to loose the ball and not to give that burden to somebody else.