1) What are you doing here? 2) What are you doing over here?
When I bump into a friend, are the two questions above all correct? If so, does "over" here imply that friend comes from another place to here?
1) What are you doing here? 2) What are you doing over here?
When I bump into a friend, are the two questions above all correct? If so, does "over" here imply that friend comes from another place to here?
Your comprehension is correct. The meaning of "over here" when talking of position or direction implies that the origin of the supposed transition is somewhat remote with respect to "here".
(looking around and not seeing) "Where are you?" -- "I'm over here!"
(from a table in the far corner) "Come over here, private!"
So, when you ask your friend
"What are you doing over here?"
, you likely mean
"What are you doing here, so far away from where I expected you to be?"
or
"What are you doing here, all the way from {the other place}?"
Such additional meaning is of course absent from the simple "What are you doing here?"