How to solve "Array to string conversion" in Laravel

I have a Multi-dimensional Array like below

quotation_country_1: ["1", "1", "1"]
quotation_institute_1: ["125", "109", "57"]
quotation_course_1: ["19", "7", "17"]

It has successfully inserted in the database but gives an error for the ajax request "Array to string conversion" So can I get help on how to solve this issue?

public function create_quotation(Request $request)
{
$lead_id = $request->post('selected_lead');

        $data = $request->all();

        if (count($data['quotation_country_1']) > 0) {
            foreach ($data['quotation_country_1'] as $item => $value) {
                $data2 = array(
                    'lead_id' => $lead_id,
                    'interestd_country_id'=>$data['quotation_country_1'][$item],
                    'interestd_institute_id'=>$data['quotation_institute_1'][$item],
                    'interestd_course_id'=>$data['quotation_course_1'][$item],
                );

                DB::table('starter_application_interested_course_ins')
                      ->insert($data2);
            }
        }
}

via Chebli Mohamed