for any country: one item will cost 5, 2 will cost 8, three will cost 13, and any additional item will cost 3 more.
For this, I have used the fallowing configuration:
Name=One item; Amount==1; ShippingWithTax=5
Name=Two items; Amount==2; ShippingWithTax=8
Name=Three items; Amount==3; ShippingWithTax=10
Name=Four items or more; Amount=>4; ShippingWithTax=1+Amount*3
Please note that "Amount" is the variable with the money amount of the order. What you really want is the "Articles" variable:
Name=One item; Articles==1; ShippingWithTax=5
Name=Two items; Articles==2; ShippingWithTax=8
Name=Three items; Articles==3; ShippingWithTax=10
Name=Four items or more; Articles=>4; ShippingWithTax=1+Articles*3
Now, The rule is not available in the cart.
It is. It just doesn't match the order, because your order probably didn't have an amount of 1$, 2$ or 3$. If you switch to using the correct "Articles" variable, it will work.
So, to my questions:
1. As far as I can understand, in order to apply condition number 4 I need the advanced plugin. Is that true?
Yes, the calculation of "1+Articles*3" is only implemented in the advanced plugin. You can, of course, list arbitrary many rules for 4, 5, 6, 7, .. articles in the basic plugin.
2. Why isnt my condition working, even after I changed condition 4 to:
Name=Four items or more; Amount=>4; ShippingWithTax=20
Because you condition on the order (money) amount and not on the number of articles...
I hope this fixes your issue.
Regards,
Reinhold