The Problem

​Here you can see the problem.

If you do not fill in all the required fields in the form on the right - when you press "submit" you get an error message below the button.

​It is this message I want to change so it is in English (and I would like to control the phrasing myself). 

I would also like to be able to adjust the "* Indicates required field" message at the top of the form.