You don’t need a translator at the beginning of the research only your intuition.
Find your client’s competitor with good SERP traffic using audit tools like SEMrush / Ahrefs .
I prefer using SEMrush for non English/ LT keyword research.
insert the competitor URL into SEMrush domain bar , Goto advance filter - Since the major purpose of this research is to find long tail keywords relating to a niche .
Select “Words - Number of words” > Greater than 3. That way you have list of keywords with minimum of 4 phrase.
Rinse and repeat for 2-3 more competitors.
Copy and compile - Have them in a translator , I prefer working with yandex . Manually check to make the LT keywords are closely related to what you want. ( QC check). You’re done!
Alternatively, if you have seed keywords for your targets , Use the Keyword magic tool from SEMrush .
insert your seed(primary) keywords into provided bar, Select “Phrase match” and that would also fetch your LT keywords for your target seed.
cc:
@cockus