Sometimes a boy's heartbreak will make him feel depressed. There are always such boys who are deeply in love, so as a friend, you must enlighten him well, let him get rid of it as soon as possible, and move towards a happier future.
Since his birthday is coming soon, why not take this opportunity to comfort him and help him have a happy birthday. Gather all your good friends, prepare a surprise birthday, make a large DIY cake, give him some small gifts, and buy a creative gift, such as a crystal ornament made of your blessings, or his own real doll, etc.
Usually let him come out to play with everyone, play ball, etc., so that he can feel deeply that there are always friends around him in addition to the surprise. I hope it helps you, and I wish my friend to get out of the darkness as soon as possible.