Widening a garage door
The professional service you need is that of a structural engineer, in combination with a contractor or builder.  Each professional has a contribution to make and can enhance the work of the other.

Internet advice does not suffice for altering structural members in a home.

You can get general advice on feasibility by posting photos annotated with dimensions.  Ensure that if you widen the door, that the garage itself is large enough that you can open the car doors (unless you enjoy exiting via the sunroof).