I tried coding the link to the form page as you indicated in an attempt to pre-select one of the form's radio buttons. Didn't work. I notice that this script is in your page. Do I need it? If so, how to configure it if my radio buttons field is API Name: dateEvent / Friendly Label: Date-Event ?
<script>MktoForms2.loadForm("//app-sj01.marketo.com", "410-XOR-673", 159,
var precheckedCategory = getQV('Category');
Category__c : precheckedCategory
You certainly need the form load script. You also need the script from the JS pane at MktoForms2 :: QS Preselect Radio
For your fields:
dateEvent : precheckedDateEvent
then include &precheckedDateEvent=<whatever> in the URL.