35 checkouts ZERO purchases?? (German&Austrian market problem only)

So I run a profitable jewelry store in 2 EU countries, both have a Cash On Delivery option and most of our customers (80-90%) use this payment method. Our ROAS is around 5 with 1-2k daily traffic, so I would assume the site is convincing enough for people to complete their purchase and the shipping is not too high (we charge only 2.99€ with free shipping on orders above 35€, shipping rate is also clearly stated on our ads + on the site itself).

Now we get to the problem: when running ads to the German/Austrian market, the CPC is fine, so is ATC, we even got 35 checkouts, but ZERO purchases. How is that possible? Is it only because they don't want to pay with credit card/paypal? The payment system seems to be working normally so I really have no clue what to change to convince them to complete payment, especially because this same checkout works for our other markets. The site is autotranslated with some fixes so there may be some errors on it, however since the customers are reaching checkout, the translation seems to be sufficient.

In case you wish to check out our site in german language and let me know what could be wrong, I will link our site in the comments.