Hello Julius,
Updates are handled by Joomla!'s extensions updater. Unfortunately it's not very robust and in some cases it completely fails to load update information without giving an error message about it. You will most likely have to talk to your host and ask them to either enable the PHP cURL module or set allow_url_fopen to 1 in their php.ini file. If they give you the very wrong excuse that allow_url_fopen is disabled for security reasons please point them to http://www.dionysopoulos.me/flicking-the-wrong-switch.html which explains why they'd be wrong.
If nothing of that helps then you most likely have a stuck update system on your site. All you can do about it is try to clear the updates from Extensions, Manage, Update and then retry to load update information. If that still doesn't help, sorry, there's nothing else we can do to help you :(
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!