Thank you, the link was both useful for me and interesting!

After reading through it, I made some more corrections to the permissions: it appeared that both the Spanish and German languages had permissions set to 700 in several places where English had 755. So I changed the permission to match them with the English language. The Zen Cart itself was installed via cPanel and the additional language packages were added through gFTP - may-be that's why the permissions were different for different languages. And as I already had a minor issue seemingly due to this mismatch, I gave the same permissions to other languages as the English language has by default. I think it's safe - unless, of course, there is some permissions-linked issue with the ZC default installation itself (which, I think, is not very likely).
Anyway, I'm just learning now and will not start with the real shop very soon. So, if I make mistakes, I can learn from them without too much pain.
One more question: content of which folders have to be translated to an another language to have the front-end completely (including buttons) in this language? 'includes' and 'admin' - sure, but what else? The back-end translation is not important. The Spanish package has three folders (email, includes, admin), the Russian package has a lot more (but as I understand, not compatible with the v1.5.1). I would need both the Russian and Estonian languages in my future store as well...
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