i send a application and i get a massege back i have existing ban history. and i don't know what they mean with that.
Eh, I'm not any part of the team that passes applications, but when they say you have existing ban history, it most likely means that you were once banned before and now they are refusing to let you back into the server. If you believe this is in error simply state so as soon as possible and I'm sure the moderators can sort this out.
That, or the weird communal registry thing where bans across thousands of minecraft servers are tracked.
Life itself. Anyway, if you we're told you have a previous ban, but you've never played here before, it's likely indeed a mcbans "global" ban from another server. I have no idea how that system exactly works. All I know is that you should probably contact SK.