If you couldn't find the strings, then you are unlikely to do the rest, as finding the strings is definitely the easiest part. Translation is a *creative* process. There are no easy recipes.
In the following firmware (fw_all.bin, in particular) every string section (there are only 3 of them) starts with bytes 4A 41 4E 00 46 45 42 00.
Obviously you will have to replace some supported language with your language, as adding a new language is too complicated.
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But in most cases replacing the strings is not enough.
In addition, you have to do the following (at least!):
1) Replace fonts if your language's symbols are displayed incorrectly. For example, american english ---> russian, you'd have to add russian symbols. A counterexample, british english ---> american english, no need to replace fonts.
2) Replace the table of symbol weights which is used when sorting strings. (In case the replacement and the replacee languages are different).
3) Edit the character capitalization and decapitalization table/function.
4) Edit the keyboard layout.
This is the things I could remember.
As you want to add a european language I'd suggest you translating the strings (replacing the englsing language for example) and then checking if everything is ok, and only then fixing bugs.