Language Editor how to start new?

Hi,
my detafult language is english and i translatet a few things there english-spanisch now i would like to have as detafult lenguage spanisch

( i tryed this then the whole network is in spanisch) but if i try there to translate, there comes up the translation that i've made before when my detaful language where inglish.

how can i delete the whole translation that i've done before? or better all what i have translatet before i want to delete and start absolutly new with the detafult language Spanisch.how can i do this? (so that the only i see is the detafult language without any translations that i've done before?) or can you do this?

widows vista, firefox 3.5.1
http://theworldofblackmen.zocku.com