@hussein10, try only a few melee tanks with the rest as ranged, that tends to work most of the way, after that when you get to the boss use a wall to keep them away while ranged goes to town on them. Rinse and repeat.
@NOkia,be sure to have mermaids in your deck, wait till your army is at max, all the while using meteor for defense, then send them all at once, the mermaids will keep knocking the goblin back while everyone else destroys the castle