Thanks for all your replies!
Okay, so when I re-use the old Multistore I get the 500 error. This only was caused by the conversion rate was not set. When I set the conversion rate it works. But this uses wrong settings (products, categories share)
So this is not a option because this all have to be done manually...
I am using a bought theme, but because I use Prestashop from 2012 and have several stores I know I have to check there what categories I can choose.
I wasn't using it in PS 1.6 anymore, I thin I break it in 1.5 or something.
I will add the screenshot from my database below. As far as I can see I am using the home as the root categorie en that's why I can't choose the Home as the main category.
I want to add a domain with the same products, categories and theme, just an other country.