Hello,

I would like to edit K2 registration form to be smaller, with just account details? Is there any way I can configure it ?

Hello Nikola,

Yes you need to override the register.php of your K2 template. Remember not to edit core files, you just have to override them,

More information on overriding can be found here.
getk2.org/documentation/tutorials/174-templating-with-k2-and-the-concepts-of-sub-templates