Slider Image & Text

Everest is beautiful, however (though I followed all the instructions) I do not manage to change the slider with the text. Though the site consists of pages, I wrote three posts and I got the ID of those posts and then I copy this ID into the field and press Save - and then the link is gone! I repeated it so often, it does not work. The site is www.das-buch-meines-lebens.de Dear Sahin, could you please explain what else I can do (besides watching this video that you recommend, but it is one hour long and starts from the very scratch and I am not sure whether it explains my specific problem at all) Thanks for helping!