Can't edit my blog

Hi there,
I'm trying to add a post or access any page of my blog but I get the message below:
Fatal error: Call to undefined function wp_get_theme() in /homepages/15/d407264274/htdocs/app413510293/wp-content/themes/colorway/functions/theme-options.php on line 11

help please!

 

Hello,
You are using old version of WordPress.
Update WordPress, It will resolve your issue.

 

How do I do that?
Is there a simpler way? I was reading the steps and it looks really complicate .. access to FTP, replacement of files, etc ..
I've never done that. Is it something I can do myself or will need to pay a specialist to do that for me?
Thanks

 

There is no need to replace files, Just go to your dashboard, There you will get update option for WordPress.
That update option will display somewhere at the top of your dashboard page.
Just click it and it will automatically update your Wp.

 

Thanks Nitesh, but there is absolutely nothing I can do with my blog. Anything I click in my Dashboard gives the message above.

 

Please send your FTP detail at [email protected].

 

Thanks.
I have sent the information to the email above.

tks!