[Answer]-Ajax response redirect

I believe you need to do something like this:

$('#form').on('submit', function(event){
    event.preventDefault();
    $form = $('#form');
    $.ajax({
        type: $form.attr('method'),
        dataType: "JSON",
        url: $form.attr('action'),
        data: {
            form: $form.serialize()
        }
    }).done( function( response ) {
        console.log('ok');
        $( '#old' ).remove();
        $( '#contact' ).append(response.content);
    })
});

You need to prevent the form submission.

Another way to do this is maybe by using jQuery Form Plugin

Next thing you should do is to add CSRFToken to your Ajax header, more on this here