GIVE ANSWERS - English

“He has fixed his car, and now he does not have any trouble with his breaks anymore.”
That is the way I would write it, the way you wrote it,
“He has fixed his car, and now he isn’t having any trouble with its breaks anymore,”
is also correct. It’s just not as proper as the first.

You could also say: "He fixed his car and no longer has trouble with the breaks." Or simply: "He fixed the breaks on his car", or if he took the car to a mechanic: "He had the breaks fixed on his car, and they are no longer causing trouble."