Can anyone with experience give me some hints? I mean is this algorithm they use successful? And is it true about having big gains?
FALSE. Arbitrage trading is meant for INSTANT profits but I guess you might have interpreted like BIG profits. Arbitrage trading is nothing but catching the gaps of price levels. No big algorithms are required but you need to watch carefully to figure out price gaps. It is like you might need to follow multiple exchanges or trading pairs and need to compare them to find an exact and perfect arbitrage trading opportunity.
Arbitrage trading opportunity may happen between an international exchange and your local exchange or within your crypto exchange but between different pairs. Hope you might have heard like Korean exchanges were trading BTC $200 ahead due to heavy local demand. This could be one real time example to understand arbitrage trading.