diff --git a/Layout/default/Calendar/Form.php b/Layout/default/Calendar/Form.php
index 8c5f60218..6304abefd 100644
--- a/Layout/default/Calendar/Form.php
+++ b/Layout/default/Calendar/Form.php
@@ -39,8 +39,33 @@
                           action="<?= self::getUrl("Calendar", "save") ?>">
                         <div class="card no-shadow">
                             <div class="card-body">
-                                <input type="hidden" name="id" value="<?= $calendars->id ?>"/>
-                                <div class="form-group row">
+                                <input type="hidden" name="id" value="<?= $calendars->id ?>"/>  <?php if (!$calendars->id): ?>
+                                    <div class="form-group row">
+                                        <label class="col-lg-2 col-form-label">Benutzer-Typ</label>
+                                        <div class="col-lg-3">
+                                            <select class="form-control" id="user_type" name="user_type">
+                                                <option value="system">TheTool-Benutzer</option>
+                                                <option value="extern">Externer Benutzer</option>
+                                            </select>
+                                        </div>
+                                    </div>
+                                <?php endif; ?>
+
+                                <div class="form-group row" id="user_select_row" style="display: none;">
+                                    <label class="col-lg-2 col-form-label" for="user_id">TheTool Benutzer *</label>
+                                    <div class="col-lg-3">
+                                        <select class="form-control select2" id="user_id" name="user_id">
+                                            <option value="">-- Benutzer auswählen --</option>
+                                            <?php foreach ($users as $user): ?>
+                                                <option value="<?= $user->id ?>" data-email="<?= htmlspecialchars($user->email) ?>">
+                                                    <?= $user->name ?>
+                                                </option>
+                                            <?php endforeach; ?>
+                                        </select>
+                                    </div>
+                                </div>
+
+                                <div class="form-group row" id="name_input_row">
                                     <label class="col-lg-2 col-form-label" for="user_id">Name *</label>
                                     <div class="col-lg-3">
                                         <?php if ($calendars->user_id): ?>
@@ -48,23 +73,20 @@
                                         <?php else: ?>
                                             <input type="text" id="calendar_firstname" name="calendar_firstname"
                                                    value="<?= $calendars->calendar_firstname ?>"
-                                                   placeholder="Vorname" class="form-control mb-2" required/>
+                                                   placeholder="Vorname" class="form-control mb-2"/>
                                             <input type="text" id="calendar_lastname" name="calendar_lastname"
                                                    value="<?= $calendars->calendar_lastname ?>"
-                                                   placeholder="Nachname" class="form-control" required/>
+                                                   placeholder="Nachname" class="form-control"/>
                                         <?php endif; ?>
                                     </div>
                                 </div>
                                 <?php if (!$calendars->id || !$calendars->user_id): ?>
                                     <div class="form-group row">
-                                        <label class="col-lg-2 col-form-label" for="calendar_email">E-Mail (optional)</label>
+                                        <label class="col-lg-2 col-form-label" for="calendar_email">E-Mail *</label>
                                         <div class="col-lg-3">
                                             <input type="email" id="calendar_email" name="calendar_email"
                                                    value="<?= $calendars->calendar_email ?>" class="form-control"
                                                    placeholder="wird automatisch aus Name generiert"/>
-                                            <small class="form-text text-muted">
-                                                Automatisch: vorname.nachname@xinon.extern
-                                            </small>
                                         </div>
                                     </div>
                                 <?php endif; ?>
@@ -226,6 +248,42 @@
     <script type="text/javascript">
         $(".select2").select2({placeholder: ""});
         localStorage.setItem('calendarActiveTab', '#user-tab');
+
+        $('#user_type').on('change', function() {
+            var type = $(this).val();
+
+            if (type === 'system') {
+                $('#user_select_row').show();
+                $('#name_input_row').hide();
+                $('#email_input_row').hide();
+                $('#calendar_firstname, #calendar_lastname').removeAttr('required');
+                $('#user_id').attr('required', 'required');
+            } else {
+                $('#user_select_row').hide();
+                $('#name_input_row').show();
+                $('#email_input_row').show();
+
+                $('#calendar_firstname, #calendar_lastname').attr('required', 'required');
+                $('#user_id').removeAttr('required');
+            }
+        });
+        $('#user_id').on('change', function() {
+            var selectedUserId = $(this).val();
+            if (selectedUserId) {
+                var selectedOption = $(this).find('option:selected');
+                var email = selectedOption.data('email');
+
+                if (email) {
+                    $('#calendar_email').val(email); // Kein readonly
+                    $('#email_input_row').show();
+                }
+            } else {
+                $('#calendar_email').val('');
+                $('#email_input_row').hide();
+            }
+        });
+        $('#user_type').trigger('change');
+
         $('form').on('focus', 'input[type=number]', function (e) {
             $(this).on('wheel.disableScroll', function (e) {
                 e.preventDefault()