"كَلْبي سَعيد."

Translation: My dog is happy.

[Ollie-Benson]

Would "My happy dog" be written differently in Arabic?

[furat-A]

It would be different. The translation would be: كلبي السعيد. Which is different in terms of stating my dog is happy as opposed to my dog; the happy one as an adjective describing its nature in general

[MehdiKebir]

ya rien de mieux.