Hello Julien, 

Thank you for your purchase.

Yes, you can try using this script for achieving that:

<script>
  var getUrlParams = function (url) {
    var params = {};
    var parser = document.createElement('a');
    parser.href = url;
    var query = parser.search.substring(1);
    var vars = query.split('&');
    for (var i = 0; i < vars.length; i++) {
      var pair = vars[i].split('=');
      params[pair[0]] = decodeURIComponent(pair[1]);
    }
    return params;
  };
  window.urlParams = getUrlParams(window.location.href);
  window.beforeConfirmBookingLoaded = function () {
    var firstName = document.querySelector("#am-confirm-booking > div:nth-child(1) > form > div.am-confirm-booking-data.el-row > div:nth-child(3) > div > div > div > input");
    var lastName = document.querySelector("#am-confirm-booking > div:nth-child(1) > form > div.am-confirm-booking-data.el-row > div:nth-child(4) > div > div > div > input");
    if ('firstName' in window.urlParams) {
      firstName.value = window.urlParams.firstName;
      firstName.dispatchEvent(new Event('input'));
    }
    if ('lastName' in window.urlParams) {
      lastName.value = window.urlParams.lastName;
      lastName.dispatchEvent(new Event('input'));
    }
  }
</script>

If you have any other questions or concerns feel free to open a new ticket and we will gladly help out.