Installing Nginx frontend in Debian server. At first, i want to say what for different Debian builds is available own the maximal revision. Example, Debian 8.0 supporting only Nginx 1.6.2 revision. For getting the actual revision you need upgrade your system up to maximal stable version (if you uses oldest version).
Also, keep in mind what Nginx server don’t updating independently and you need updating manually. Before updating you need delete the old version (do backup all configs) and after to install the new version and restore backup.