<a href="https://api.whatsapp.com/send?phone=62895325535522">
<img src="https://hantamo.com/free/whatsapp.svg" class="wabutton" alt="WhatsApp-Button" />
</a>
<style>
.wabutton{
width:40px;
height:40px;
position:fixed;
bottom:20px;
right:20px;
z-index:100;
}
</style>