Hou can i list the last 5 post's from the composer in a page?
You can use the Pagelist Block (core) or the Pagelist Title block in Marketplace etc.
If you want in all pages, edit in Dashboard > Pagetype > select your_page assigned in composer > Edit > insert the block in required area > Save.
If you want in any page, go to the page and click edit > add the required block above.
Hope this is what you described.
You can also look thru the Marketplace with an add-on for blog thumbnails (if not mistaken). It's a block/template with same functionality with associated page publish date and description as well as title.
Or, are you well verse with php/html and creating override custom templates for concrete5 Pagelist or any blocks? And you also have access to your files via FTP where you host your c5.