[Seorsum]

ok Can you take a piece of an private realm and turn it into an public realm? this is my question

Nope.

[MrKeveCool]

ok sad but it should be really useful in this server

[volcomboy98]

ok sad but it should be really useful in this server

Not at all, because the reason your buying a realm is so it's private, but you want to make it public? Just go use a public realm.

[planephanatic]

ok sad but it should be really useful in this server

It will most likely be a feature in the future. (See here.)