Protagonist is an old cultivator that reincarnates/ transmigrated to modern times. Don’t remember much but he frequents a small restaurant that one of the school belles works at and her family owns. His fat friend falls for this girls friend who is in a wheelchair I think, his cousin ‘played with the girl’ , the girl jumps out the window to kill herself and protagonist pushes friend to catch the girl, and they end up going to this friends family gathering. Hope that’s enough
I think it is Beauty and the Bodyguard (https://www.novelupdates.com/series/beauty-and-the-bodyguard/) but he didn't transmigated, maybe you remember that part wrongly?
This is probably it. He didn't transmigrate but inherited an ancient cultivation method? The friend is ordinary but his uncle is a "miracle doctor" that came out with a special medicine, so the friend's cousin dated the girl, sexed her up and dumped her so she went a bit crazy, and I think he even tried to hire people to harm her, so she had a limp or something? MC catches her when she jumps off build then they go to hospital where his friend falls in love with her.