Is there any cost in the use of the NYNJA marketplace? If yes what is it and how does it work?
Yes there will be a small fee for the freelancer marketplace depending on the project.
Can you please shed more light on the NYNJA protocol?
That is best explained in our whitepaper which you can find here:
https://nynjacoin.io/documents/english/NYNJA_whitepaper_EN_v20_2.pdf