So, it is not a free mixing service. Right?
Also, what are the minimum & maximum value that you can mix at one go?
Minimum 0.001 BTC + additional 0.00001126 BTC for each output address. In total, for one output address it is 0.00101126 BTC, there are no restrictions on the number of mixed bitcoins, you can get acquainted with this simply by reading the expanded version of the FAQ
https://yomix.io/en/pages/faq the mixing fee ranges from 0.7% to 5%