Can't import / export translations, constant errors

[Inur]

I'm pretty much used to encountering errors on every single step in Prestashop but with this I'm stuck because not a single function works. 

 

Trying to import a Polish language pack from my old store on PS 1.5.4. Now running 1.6.1.1

 

Add/Update language: 

> The translations have been succesfully added.

Result: nothing. Still not a single translation.

 

Import a language pack manually:

> Validation failed for: mails/pl/lang.php

> Imported official pack from Prestashop. Succesful but NOTHING has happened. 

 

Export a language:

> 2 errors 

1. An error occurred while creating archive.
2. Please select a language and a theme.

Both of which I have done, obviously. 

 

Modify translations is the only function on that page that works. So I would have to manually translate 1000+ fields to get my shop back in the language I use it in. Surely there is an easier way?

 

I'm using Megastore theme.