I would be happy to help but I am not exactly sure I understand what you are looking for. To clarify, based on your forum title, it sounds like you are trying to locate a specific app. If so, what kind of app are you looking for? Or are you having issues with your shop?
When following the link you shared, this is what I see:
It seems to be taking me to a page that no longer exists but after some digging on this shop, I think I may have found the product page you were trying to share: "https://www.sygns.de/products/neonschriftzug-selbst-gestalten-leuchtschrift". This URL is very similar to the one you shared, but it looks like your URL was missing the "T" at the very end. Anyhow, if this isn't your shop, are you looking for an app that helps create this product simulation as shown here?:
If you can share a little bit more information about what you're looking to achieve, I would be happy to continue helping!
Sunny | Shopify Guru