Increase number of thumbnail image and add arrow

Good Morning im struggle with a problem in shopify i use Flex theme, i add the Thumbnails

in product information under the product image

but i cant find in the code where to change the limit ( max is 5)

same for add arrow (if is possibile)

the arrow that i try to add are here (thats an example page for understand where the right place for the arrow) but it doesnt work in the website

https://sino-swiss.myshopify.com/collections/burotisch-twin/products/kopie-von-elektrisch-hohenverstellbarer-burotisch-eiche-natur-1?variant=45596203090175

someone has an idea?

Hello @Olaf5

You can try to follow these steps:

Go to Online Store → Themes → Actions → Edit code.

Go to Assets folder → styles.css

Add the following CSS at the bottom:

@media only screen and (min-width: 799px)
{
     .product-gallery .flickity-prev-next-button 
{
           opacity: 1;
           visibility: visible;
           padding: 0;
     }
}

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Hallo unfortunatly doesnt work properly, if i click the arrow he doesnt change the image