Sale Banner disappears as soon as you click on different variant

[ShockNIA]

So I have added a sales banner to my shop with CSS/HTML + changed the CSS from the price a little, but as soon as I click on a different variant all the CSS/HTML changes I made a disappearing. 

My shop: https://alerina.de/products/fleece-strumpfhose-angebot?_pos=1&_sid=f800cd32d&_ss=r