How can I pass the data to 2 tables in same function

I need to pass same data to 2 tables(prospect & course_prospect)

This is my function

public function store(Request $request) {

    $prospect = new Prospect;

    $prospect->prospect_name = $request->prospect_name;
    $prospect->prospect_nic = $request->prospect_nic;
    $prospect->contact_number = $request->contact_number;
    $prospect->address = $request->address;
    $value = implode(',', $request->course_intrested);
    $prospect->course_intrested = $value;
    $prospect->comments = $request->comments;
    $prospect->referred_through = $request->referred_through;

    $selected_courses = new Prospect;
    $course_prospect = new Course_prospect;

    $course_prospect->course_id = $value;
    $course_prospect->prospect_id = $selected_courses->id;

    $course_prospect->save();
    $prospect->save();

    return redirect()->back();
}

and the course_prospect table have 2 foreign keys(course_id & prospect_id )

This is course_prospect migration

    Schema::create('course_prospect', function (Blueprint $table) {
        $table->engine = 'InnoDB';
        $table->increments('id');
        $table->integer('prospect_id')->unsigned();
        $table->integer('course_id')->unsigned();
        $table->timestamps();
    });

    Schema::table('course_prospect', function($table) {
        $table->foreign('prospect_id')->references('id')->on('prospect')- 
                >onDelete('cascade');
        $table->foreign('course_id')->references('course_id')- 
                >on('course')->onDelete('cascade');
    });

but when I submit my form prospect table only having data. I think foreign key is not working

via Chebli Mohamed