Hello Chouby,
thanks for your reply!
We have 4 languages on our site, after I run your script, it creates another 4 posts of "polylang_mo" type, so I have totally 8 posts there... I deleted all posts with post type = "polylang_mo", then run your script and it looks like new posts have been successfully created and on database everything looks fine, there are all pairs of "string - translation".
http://www.pixhost.org/show/2089/27585212_polylang-db.jpg
However, I am still not able to edit strings on Settings > Languages > Strings translation, all strings are still there on English.
http://www.pixhost.org/show/2089/27585215_polylang-wpadmin.jpg
Any ideas what is wrong? Is it problem that I changed IDs of posts?
Thank you in advance for your reply.
Michal