Feed without tax

Can you please tell me how you calculate the VAT so that i can suggest you?

i let woocommerce do it for me:
woocommerce / settings / tax(options)

This option is not available with our free plugin. You have to add price including VAT using Dynamic Attribute which is a premium functionality of our Premium Plugin. Please check our website https://webappick.com/plugin/woocommerce-product-feed-pro/

Ok so in the video of:
https://webappick.helpscoutdocs.com/article/20-how-to-make-dynamic-attribute
On 2:07 min, ill do:
“regular price” “greater than” “1” “pattern” “+21%”
(i have no products less than 1 euro in price)
21% tax for the Netherlands)
Problem solved, right?

Yes. Exactly. You are right.

I am getting a Internal Server Error if i try the above.

Go to the link below and open a support ticket.
https://webappick.com/support/