I put a camera 2d as a child node for my player :
and here's what i see
any idea how to fix that?
Cameras usually work better on the same level as the player. You can set the follow to enable and add an offset if needed.
I think what you need is a script on the Camera like this:
var player = get_node(".../Player")
position = player.position
Then on the camera, enable smoothing and you can adjust the offset on the right in the inspector.