the file we need to translate is called stringtable.xml inside have a lot to translate but one time is translated to our mother language will works for all this russian mods. (keep it / backup it after translate because is a lot of work xD )
this one is from the last LOTD that have the selection menu in english but you can modify the stringtable.xml for the others msg appears in the game.
stringtable.xmlbackup the stringtable.xml that is located inside the root of the mission and paste this one. now delete you savegame that is located in mydocument >arma2>saved and start a new game.
if you want to translate the rest of the text you have to use google translate or other tools like that and inside this file stringtable.xml you will find a lot of text like this
<Key ID="SPP_chat_83">
<Original>%1 Выходи по хорошему, иначе разговор будет короткий!</Original>
<English>%1 Выходи по хорошему, иначе разговор будет короткий!</English>
<Russian>%1 Выходи по хорошему, иначе разговор будет короткий!</Russian>
</Key>
replace for example "Выходи по хорошему, иначе разговор будет короткий!" for the text in your native language. for example i make this example in english.
<Key ID="SPP_chat_83">
<Original>%1 Get out for good, otherwise the conversation will be short!</Original>
<English>%1 Get out for good, otherwise the conversation will be short!</English>
<Russian>%1 Get out for good, otherwise the conversation will be short!</Russian>
</Key>
that is the easy way i can find to translate it. remember you need to start a new fresh for to see the changes.
not all the russian text appears in the game are in stringtable.xml but for now is a good start. happy translating!