Hideout upgrade

hi, i am currently using a haku-hideout and he is close to level 6. but what happens then? when i upgrade my hideout will i have to decorate it new? or can i upgrade and the decoration just stays but i get more space?

ps: sorry for bad english - foreigner here ;-)

When Haku reaches 6 you just talk to him and choose the create hideout option. You will then be ported to a new hideout with increased size, nothing in there.
Claim the hideout and then all your decorations and masters will be ported in, merged in the new hideout size.

Don't be scared when you see an empty hideout when you create. Just claim and you'll see.

If you already have a hide-out and you just want to upgrade it when he hits level 6 you don't create and claim a new hideout! It will ask you if you want to upgrade, and you just hit yes and you hideout grows...you only need to create and claim a new one if you aren't happy with the current master's hideout!