I have .30 BTC, If i signed a messages for you, How much you will pay to me?
Apperantly 0.0012 BTC, but if i was you i would ask him to pay first because you have been much longer here.
You can also get byteball by yourself and sell it for BTC if you'd like, here is the link
https://byteball.org/It is pretty simple thing to do.
Wil you elaborate it please? Actually how can i do that? I have visite byteball.org but what i have to do there?