That means you can use even a third language!? Or am I wrong?
Thank you for reporting!
P.S. One error in Installation description:
2. In Configuration tab, copy.paste code below in "plugin configuration" fields
&defualt_lang=default language;string; -> must be &default_lang=default language;string;
By this correction, [%LANG%] always has value and when you set default language to German, the TV will be [*decontent*] by default.
But in case then it just http://domain.tld/site/sitelink.html - [*[%LANG%]content*] has a previous [*content*] value.
I re-uploaded it
...I can’t unzip the zip!? Error!!

But in case then it just http://domain.tld/site/sitelink.html - [*[%LANG%]content*] has a previous [*content*] value.
By this correction, [%LANG%] always has value and when you set default language to German, the TV will be [*decontent*] by default.
Plugin sets value of "&lang" query as a _SESSION (cookie) so you will see page in the last language you’ve choosen when removing &lang.
It allows user to choose his/her language once and review pages in own language.
Was it your problem or i am wrong?

<a href="[~[*id*]~]&lang=en">English</a> <a href="[~[*id*]~]&lang=fa">Persian</a> (default)