Ok so first, go to the login page, click the Session Storage Manager, click Define Session Storage Items, make sure under sessionStorage you have sessionusername as a number then replace the body tag of your code with the following
<body id="Dr Kade login" is="dmx-app">
<dmx-session-manager id="session1"></dmx-session-manager>
<div is="dmx-browser" id="browser1"></div>
<div class="container wappler-block pt-3 pb-3">
<div class="row">
<div class="col-12 col-xl-4 offset-xl-4 text-center bg-light p-5 col-md-8 offset-md-2">
<img class="wappler-type-user mb-4 img-fluid rounded-0" width="200" height="62" src="assets/images/logo-drkade.jpg">
<div class="contentArea">
<p class="font-weight-bolder text-info"><b>„Untenrum“ gut beraten</b><span is="dmx-typed"></span></p>
</div>
<form id="form1" method="post" is="dmx-serverconnect-form" action="dmxConnect/api/users/login.php" dmx-on:success="session1.set('sessionusername',username.value,{});browser1.goto('select_hotel_form.php')">
<div class="form-group" id="kade_login">
<label for="username">Username</label>
<input type="number" class="form-control" id="username" name="username" placeholder="Enter Your Username">
</div>
<div class="form-group" id="kade_login1">
<label for="password">Password</label>
<input type="number" class="form-control" id="password" name="password" placeholder="Enter Your Password">
</div>
<button class="btn btn-primary" type="submit">Log in</button>
</form>
</div>
</div>
</div>
<script src="bootstrap/4/js/popper.min.js"></script>
<script src="bootstrap/4/js/bootstrap.min.js"></script>
</body>
Next on your second page, first click the Session Storage Manager, click Define Session Storage Items, make sure under sessionStorage you have sessionusername as a number then replace the body tag of your code with the following.
The reason I am asking you to double check this is because I found a reference in your code to usernamesession and not sessionusername
<body id="show_hotels" is="dmx-app">
<dmx-serverconnect id="userdetails" url="dmxConnect/api/users/userdetails.php"></dmx-serverconnect>
<dmx-session-manager id="session1"></dmx-session-manager>
<img src="assets/images/logo-drkade.jpg" width="283" height="88" alt="Dr. Kade" id="drkade" class="img-fluid img-thumbnail">
<dmx-serverconnect id="connectionkade" url="dmxConnect/api/get_hotels/hotels.php"></dmx-serverconnect>
<main>
<div class="d-flex text-center flex-column">
<p> :</p>
<p><b>Herzlich Willkommen, liebe Apotheke </b></p>
<p><b>melden Sie sich für eine der folgenden Veranstaltungen an:</b></p>
</div>
</main>
<table class="table table-striped table-bordered table-sm text-center w-100">
<thead>
<tr>
<th class="w-auto text-center">{{session1.data.sessionusername}}Event</th>
<th class="text-left w-25">Eventhotel</th>
<th class="text-center">Eventdate</th>
<th class="text-center">Eventday</th>
<th>Eventcity</th>
</tr>
</thead>
<tbody is="dmx-repeat" dmx-generator="bs4table" dmx-bind:repeat="connectionkade.data.queryhotels" id="tableRepeat1">
<tr>
<td dmx-text="event_id" class="text-center"></td>
<td dmx-text="event_date.formatDate("dd-MM-yyyy")" class="text-center"></td>
<td dmx-text="eventday" class="text-center"></td>
<td>
<a href="#" dmx-bind:href="mykade_events.php?event={{event_id}}&pharmacyid={{session1.data.sessionusername}}&eventhotel={{eventhotel}}&eventdate={{eventhotel}}&eventdate={{event_date.formatDate("dd-MM-yyyy")}}&eventcity={{eventcity}}">{{eventhotel}}</a>
</td>
<td dmx-text="eventcity"></td>
</tr>
</tbody>
</table>
<div class="content">
<main class="text-center font-weight-bolder w-75">
<div class="table-responsive">
<table class="table">
<thead>
<tr>
<th scope="col"></th>
<th scope="col">
<p>Hinweis: Sie können insgesamt 3 Kollegen anmelden und 2 weitere auf die Warteliste schreiben. Wir melden uns so weitere auf die Warteliste schreiben. Wir melden uns so schnell wie möglich bei Ihnen, ob Sie einen festen Platz bekommen.</p>
</th>
<th scope="col"></th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row"></th>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<th scope="row"></th>
<td></td>
<td></td>
<td></td>
</tr>
</tbody>
</table>
</div>
</main>
</div>
<script src="bootstrap/4/js/bootstrap.min.js"></script>
<script src="bootstrap/4/js/popper.min.js"></script>
</body>
If something does not work right away, please make sure both files are saved and you have refreshed a few times, or rather close the browser window and reopen, to make sure the previous sessions have been cleared.
If still something wrong, tell me before trying to fix rather so I can check please.
The only thing I was unsure of was a class on your first table of mw-100
, I think it is possibly meant to be just w-100
but dont know if you have a custom style for that, so left it alone.