You have not merged the profile, but added it as a child to Hans (created a link or connection). Easy to do, and undo.
07:28: Ron Reiman added Anders Hansen (1736-1812) as child for Hans Rasmusson (1701-1773). [Thank Ron for this]
There is no such thing as 'my tree', there is only one tree with connections. If this connection is wrong, you can undo it. Go to edit on the profile, you will see the father on the top right with the option to replace/remove it.
Click that, scroll all the way down and click 'remove Hans as...' That will remove the link.
Merging is the process of making 1 profile out of 2, which is more harmful.
Note that the profile you link to is unsourced, if you have any please add them or add the unsourced templated to the profile.
