There must be an easy way to do this… but I’m messing up my project for more than 2 hours now 
I managed to rule the tempo track following the recording, now I simply want to delete the first 3 bars. Result should be: bar 4 becomes bar 1, recorded applause comes in that first bar and the song starts exactly 2 bars later (now bar 6).
Use the range tool
Many thanks Janostudio.
So the solution is:
- select the range to delete
- menu Edit
- Range
- Delete Time
If the object tool is selected (the usual choice when working):
- Set the left and right locators for the range to be deleted;
- Hit
Shift + Backspace.
An easy way to do this is to select the range and hit “P”
That sets the locators to the borders of the selection.
But the delete range command is faster, I guess.