Hello,
1) go to Theme Options > Header builder > edit the search element and change texts https://prnt.sc/zlzddq
2) Contact Polylang author to find out why they don’t load translation for the mini-cart, as I can see it does not work even with the default theme https://prnt.sc/zm15f3
We found the following answer from the Mailchimp author about the translation of their form using Polylang https://wordpress.org/support/topic/polylang-and-mailchimp-for-wordpress/ So, ask the Polylang authors if they have any other solution for this.
3) Contact Polylang support about the translation of the WooCommerce pages and products. I suppose you need an additional plugin for this https://polylang.pro/downloads/polylang-for-woocommerce/
Regards