I can't get the page to display my translation

Hi everybody, I am trying to make the J&E plugin to display in German.

I did the translation for the frontend with poedit and uploaded the mo and po to the plugin's lang file.

In the wp-config.php I added the WPLANG define line.

But it just will not show in German.

See here for an example. It should read "Registriert seit" instead of "Member since". That's just one of the translations I made.

I'm confused.

Plus, I want to use the Experts as a list of participants. Is there any way to rename the slugs in a way that will not be overwritten when the plugin is updated?

Thank you!