I have assigned some Office 365 E3 licenses for people from different regions at my company. These regions should be able to have access to one particular subsite on a sitecollection in my intranet, but at the same time not having access to the rest of the intranet (my other sitecollections, and subsites). How can i solve this?
If you navigate to the site you want to give them access to select site sittings > site permissions.
Click on Create group and create a group called "Region access" or something suitable. Click on this new group and click new to add the users.
Because you created this group on the sub site the users added will not have access to other areas.