Percentage of Total based on Dynamic Filters (Sum = 100%)

Hello everybody,

I try to rebuild the quick calculation "Percentage of total" in a new measure.

Measure = 

VAR Volume =
   '2_komplett'[Sessions]
VAR AllVolume =
   CALCULATE('2_komplett'[Sessions];ALL('2_komplett'))

RETURN
    DIVIDE ( Volume; AllVolume )

As long as I do not use any filters the result is just the way I want it to be (below both percentages next to each other, '%SG: Sessions' is the result of the quick calulation):

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But as I use a filter (eg country, device) my measure still adjusts to the grand total. I want my measure to adjust to the filter (filtered value is new total ---> Sum is 100 %) - just as the quick calculation.

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Does anyone know the solution to my problem?

Thanks in advance