Yes. "-ся" is attached to the verb. In this case боятся (bojatsja) "they are in fear of."
But cię is the short form of ciebie in Polish. This translates as тебя (tiebia) in Russian, and there is no short form.
Thanks for your frequent helpful comparisons of the differing but sometimes similar Polish and Russian. At 16 I briefly tried to teach myself Russian (alphabet, pronunciation, and a little vocabulary), so it's interesting to know what I missed out on.
You're welcome. The similarities and differences between Polish/Ukrainian/Russian fascinate me.
Short forms don't exist in offical writing, yet they do exist is casual speech.
For example: Чё те надо? / Я тя не узнал.