Hello,
Yes, I'm using default-bootstrap theme, and yes I chosen default-bootstrap when imported translation in Back Office, this is the only theme I have, but inside /themes/ there is 'default' and 'default-bootstrap' folders.
I have tryed to extract lt.gzip and open with Notepad++, so I believe there is only Back Office and some modules translations.
As it starts with:
global $_LANGADM;
$_LANGADM = array();
$_LANGADM['AdminAddressesd3b206d196cd6be3a2764c1fb90b200f'] = .........
......
And below there is some modules translations I believe.
SOLVED: I copied /themes/default-bootstrap/lang/lt.php file from older PS 1.6.0.5 installation to PS 1.6.1.6 and now it shows translation in Frontend.
So I have solved my problem I guess, but I have no idea why this translation was missing, because according to https://www.prestashop.com/en/translations PS 1.6.1.6 Lithuanian translation is completely translated (100%).