I looked at your index.html and I only see where you passed in your user ID. Can you post the part where you have to pull the form data from the html inputs and append them to a new Form object? This is more or less the main side of the code, I used jQuery to handle it. Example.

 $('#contact-form').on('submit', function(event) {
    event.preventDefault(); // prevent reload
    
    let formData = new FormData(this);
    formData.append('service_id', 'default_service');
    formData.append('template_id', 'template_mezfpy6');
    formData.append('user_id', 'user_ID');
 
    $.ajax('https://api.emailjs.com/api/v1.0/email/send-form', {
        type: 'POST',
        data: formData,
        contentType: false, // auto-detection
        processData: false // no need to parse formData to string
    }).done(function() {
        console.log('Your mail is sent!');
    }).fail(function(error) {
        alert('Oops... ' + JSON.stringify(error));
    });
});