Hi muharrembas,

I see you set thumbnail’s width to 70px, which seems small but it worked https://prnt.sc/9DxhIiT2tarx

Also, you can set Thumbnail size in Customize > WooCommerce > Product Images as well

And remove your Custom CSS code related to Single product image and add below code to Theme Settings > Custom CSS > Global section

.woocommerce-product-gallery img {
    width: auto;
}

Let me know how it goes.

Regards,