when i create a new blog with a new template group it is empty. no posts from my old weblog are inside. what i must change that i see all old posts in my new blog?

Well, what are you trying to do? Just change the design of the old blog?  Moving posts to a new blog isn’t really possible inside EE atm, it would take SQL queries and a lot of care.

i wish to change the name weblog into a new one. but when i change all in admin, in teplates and so on, than i run in trouble. i thought it is easier to change all. create a new blog

Change the name of it, that is all you want to do?  Just change the long name in admin -> weblog prefs and don’t touch the shortname.  Noone will ver now the shortname, other than you, anyway…

and urls too? is this easy way realy working?

it is easier. i must only change the template group name and than urls. is so easy and i am testing all soooo long. argh