Blog not working

Dear all,

we are used using our website only with static pages until now.
Now we need to create a blog page and we are dealing with a problem that we can not solve. We hope to get support from any of you.
Many thanks in advance!

Problem:
We can add new post on the dashboard, but these dont appear on the blog page. The post entry list is showing on the widget, but ás you click on one entry the page appears empty.

Any idea?