Duplicate contact when i log with this one
You can dedupe contacts in two ways in CiviCRM. 

The first one to do a search and find both contacts and then check the checkbox in front of both contacts and select the Merge Contacts from the action list (screenshot is in Dutch).



The other way is from the dedupe functionality under the Contacts --> Dedupe menu.

You have to select a rule and it will try to find matching contacts which you could then merge.