>> This has nothing to do with the database, this is just strings to be translated an showed in the screen.
It may not have anything to do with the database, but it has everything to do with the setting, and from that setting, how things work.
>> If I need to have a server to serve different languages, AFAIK I need utf-8, not only Spanish.
It depends on the languages. Spanish falls under "western europe" so covers spanish, english, french and so on. However once you go further out (Scandinavia, Central or Eastern Europe and so on) then it becomes better to store as utf-8.
Unfortunately storing as utf-8 though means "no reports", because clarion reports don't yet do utf-8. Well, you can have reports but extended characters will appear funny.
So if you need reports then it's best to choose a charset, if you can live without reports then it's best to use utf-8.
Whichever one you pick, you then need to manage the rest of your inputs to match. For example you are loading a value from an INI file, so this value must be encoded one, or other way as well. Plus where you use it matters - items passed through the translate method will be converted from "save as" to "charset".
Lastly, you need to manage template settings in the IDE - things you type into the IDE tend to be in a charset, not utf-8.
So, in summary, to make it work you need to know, and manage the encodings from all your sources and make sure it's in the right encoding in the right place, to match up with the "charset" and "save as" settings. When you have decided which settings you want to use then let me know and I can give you more direction as to what to do to match those settings.