Populate field depending from Dropdown list in Acrobat Form

Hello there,

I am not a coder and I'm trying hard to understand... but I need anywayyour help because I can't understand what's the solution.

I need to create a form where, when one value is selected from the dropdown in "column B" it will automatically populate a certain value in "column A".

This is something that I need to do many times in the same form, morover, I need to make a final addition with all the prices to get the Total amount (this one I think I understood how to do it)

Can you help me??

Thank you!

Chiara