Uploading files to poedit and translating them after update plugin

I can not upload files to poedit i got a message the file is corrupted? can you tell me what i must do? i need to use poedit because there is an update for membership plugin which means that my translated dutch language files will be overwrited by the original english ones. Can you tell me how to use poedit in order to have the duch translation again. If i understand it well i must first open the new englisch membership-en_EN.po with poedit and then go to catalogus/edit from pot file and select there the old dutch pot file membership-nl_NL.pot that i had stored this will translate membership-en_EN.po with the old membership-nl_NL.pot file and keep the new strings that a can manualy translate is that correct?