@Fernandotf I just visited that exchange and at first glance I could see that it is a disaster from start to finish. Oversized images, slow loading of the main page when almost everything is text... And the most curious thing of all, I don't know if it is due to IP blocks in my country, but I have not been able to access it from clearnet, I have had to use Tor to be able to see the exchange, which makes no sense.
As for the 4% that they demand from you on profits, it seems absurd to me, but that is something that you should have found in the ToS of the exchange before starting to use it, if that condition does not appear they do not have the right to ask you for that percentage.
The domain is registered since:
Registered On: 2012-05-18
In 2012 in that domain they talked about iPhone, in a language (I don't know if it's Japanese or Chinese) that I don't know. On this website you have more information:
http://web.archive.org/web/20130407100643/http://www.szios.com.
The best thing you can do is try to withdraw your funds from that exchange, never use it again and start using another one, preferably decentralized, where you will not have these problems.