a lawyer will cost me a lot of money for this case?
are there lawyers who only get payed by reward if the case is won in my favor?
You have 500
BTC stuck in exchange which are currently worth 3,837,000$, and you only think how will some lawyer cost you a lot?How much is lot for you,100 000$,300 000$ or more?But if this is only way to get that coins back you do not have to think too much.
Try to find a lawyer in your country,in the first place for easier communication,and if you do not succeed in that obviously you will need foreign assistance.Second best option is to find Chinese lawyer,just because Bitfinex is Hong Kong based company.
Try to use search engine for cryptocurrency lawyer//I just find this one:
Cryptocurrency Lawyers