Hi Hyyan,
I have a similar problem with some strings not translated in just “Shipping” and “Payment” and everything else seems to be working ok. There’s multiple shipping and payment options enabled and it appears only the first option is translated and not the rest.
Ex. Shipping: Free Delivery (translated), Local Delivery (not translated) and etc. Payment: Bank Transfer (translated), Cash on Delivery (not).
I installed and activated the plugins in the following sequence; woocommerce, polylang, hyyan woocommerce and then added the languages.
Thanks.