how to use arr in fetching belongstomany model in laravel code example

Example 1: how to use where relationship laravel

Event::with(["owner", "participants" => function($q) use($someId){
    $q->where('participants.IdUser', '=', 1);
    //$q->where('some other field', $someId);
}])

Example 2: laravel pivot table model

/*Model - Service*/
public function customer(){
    return $this->belongsToMany('customer')->withPivot(
        'start_date',
        'stop_date',
        'rem_date',
        'due_date',
        'status'
        );
}

/*Model - customer*/
public function services(){
    return $this->belongsToMany('Service')->withPivot(
        'start_date',
        'stop_date',
        'rem_date',
        'due_date',
        'status'
        );
}

////These following relations didnt workout
/*Model - custserv*/ //uses the pivot table customer_service//
public function staff(){
    return $this->belongsToMany('Staff');
}

/*Model - Staff*/
public function custservs(){
    return $this->belongsToMany('Custserv');
}

/*schema for pivot table 'staff' and 'Custserv' */
Schema::create('customer_service_user', function(Blueprint $table)
    {
        $table->increments('id');
        $table->integer('customer_service_id')->unsigned()->index();
        $table->foreign('customer_service_id')->references('id')->on('customer_service')->onDelete('cascade');
        $table->integer('staff_id')->unsigned()->index();
        $table->foreign('staff_id')->references('id')->on('staff')->onDelete('cascade');
        $table->timestamps();
    });