I was looking everywhere for czech subtitles for HoMaM IV but unseccesfully. Any way, how to add cz subtitles from czech version to gog version? Or maybe someone knows where can i download cz subtitles?
I can play it in english but i prefer czech for RPGs, it is much easier and faster to understand.
So if someone can help me, i will be so grateful.

Since HoMM4 in Czech Republic/Slovakia was sold already translated, I doubt that you will find any translation.
The only possible way would be to get a Czech version and try to fiddle with replacing files until you get the translation in the game.
I can't help you anymore, because I gave my translated retail version to a friend after I got the GOG version.

Agree with klaymen, there isn't any community-based translation.
It'd be possible to patch the GOG version with the czech retail version from CDProjekt (which came with czech version of Heroes 1 and 2 as well, btw) but since they worked on a localisation from scratch (eg. got the sources from 3DO and compiled/repacked everything), there are probably too many differences between the two. I think you're better off getting the czech version elsewhere and installing it instead. I got it years ago and it doesn't seem to be DRM'd. It also works quite fine on Windows 7.

There have been some questions about czech versions of GOG games on czech CDP forum but from what I've gathered the connection between the czech branch and GOG guys is quite loose and CDP-Czech only had rights for local distribution, so they couldn't share with GOG even if they wanted. And since the company has been bought by someone else and became totally independent from CDP some time ago, I doubt we'll see any legit czech versions of their games on GOG.

Thanks for replies guys. I think i will practice my english. It's better than download another version in CZ localization :-)