Hello,
1) I see some issue with the saving of the WooCommerce plugin translation https://prnt.sc/uST7AJGmB40b So, contact your hosting provider and ask to fix the issue with the permissions to allow you to Sync translation and save your changes.
2) Add the below code if you want to hide that
.checkout .cart-order-details .e-coupon-box {
display: none !important;
}
Regards