Hi,
1. The product code in the cart module is only displayed if the "show product code" setting is activated in the HikaShop configuration.
If you don't want to display the code anywhere, you could just turn that setting off.
If you want to hide it only in the cart module, you can add such CSS in your website:
.hikashop_product_code_cart { display: none; }
2. It's likely not a translation issue but the name of the tax rate that you used in the "manage tax rates" area of the System>Taxes menu.
Now, it's also possible to enter a translation key as a tax rate namekey and then add your own translation override for it.
So since your tax rate namekey is currently BTW, you could add such translation override:
BTW="BTW incl"
Or you could create a new tax rate with the new name and then change the tax rate used in your tax rules to the new one with the name you want.