I found out how to get the first item from a collection:
$pageId = Mage::getModel('cms/page')->getCollection() ->addFieldToFilter('identifier', 'your name in the pages') ->getFirstItem() ->getId();
But now I have 3 IDs with the same name but different store views. How can I get these item-Ids? When I write that statement above without "getFirstItem()" and/or without "getId()" then Magento throws me an error.