<script src="https://cdnjs.cloudflare.com/ajax/libs/iframe-resizer/4.1.1/iframeResizer.min.js"></script>
<div>
<iframe title="Live booking" id="brm-online-booking" src="https://app.bikerentalmanager.com/book.html?shop=tawebikes&iframe_resizer=4.1.1" style="width: 1px;min-width: 100%;" frameborder="no" scrolling="no"></iframe>
</div>
<script type="text/javascript">
iFrameResize({
                heightCalculationMethod: "taggedElement",
                checkOrigin: false
}, '#brm-online-booking');
</script>