“An emerging artist comes to town to become an art star, but it won’t be easy for him, there he falls in love with a promising young lawyer. A car accident leaves the couple in a coma, only one can live thanks to the heart of the other, and thus be able to fulfill their dreams. ”

It sounds interesting but I'm not clear why the one with the good heart would give it up.

Some options to consider:

What is the inciting incident? Perhaps it can start from when the heart transplant happens

Maybe have a heart donation available from a third party but only one can get it so it becomes a legal case. What are the stakes/consequences?

Perhaps the artist is brain dead but has his heart functioning thus donating his heart to the lawyer.

What is your theme? Where is it going?

Does the story end with the heart transplant

or

does the story begin with the heart transplant

I can't tell from the way this is written. (Although I like this better than your first attempt)