I did something stupid similar to this question: Stackoverflow question
Let me summarize it quickly:
I created a branch1 from master - did some changes - then created a different branch2 from master to do a hotfix - then i did a rebased branch1 onto the hotfix/master - and I got duplicate commits in my branch1.
Now I know i should've merged it - but how can I undo these changes? Here's a Picture of how it looks - the red rectangles are the duplicates.