How to paginate a single-Tag Archive Page

Hi there!

I created a page which displays all the posts under a specific tag: “Featured”. I would to paginate the appearing posts (5 posts per page) and to show the posts_nav_link at the bottom of the resulting page. I have read here, have grabbed that code and transformed it into this one.

But I receive this error:

Parse error: syntax error, unexpected ‘<‘ in /web/htdocs/www.aldolat.it/home/wp-content/themes/myclass/featured.php on line 38

Line 38 is the fourth in the link above.
How can I fix this?
Thanks in advance. ??

P.S.
If instead I try this code, WordPress outputs correctly the required posts with navigation link, but – although this link links to page 2, page 3 and so on – the resulting displayed page is still the same and the URL is /page/2, /page/3 and so on.
You can view this page here.