Move Excel calculations to Power BI - specific help in measure creation

I am transforming an excel calculation sheet into a power BI dashboard and need help in creating the correct measures.The content is an analysis of testresults, so all measures should only calculate the filtered table in the screenshot.
I also added the relationship as the fact table (Testresults) will be filtered and the dimension (Gesamtliste) should provide details per "index" by slicers and the visibly content should be calculated.

The measures that I use look like this:

fck = CALCULATE(AVERAGEX(TestResults, RELATED(Gesamtliste[Festigkeitsklasse])),ALLSELECTED(TestResults[Lifex]))

m(fci) =
CALCULATE(
AVERAGEX( SUMMARIZE( TestResults,TestResults[Index],TestResults[Wert]), TestResults[Wert] ),
ALLSELECTED( TestResults[Wert],TestResults[Lifex])
)

MW-Transf. = CALCULATE(
(AVERAGEX(TestResults,TestResults[Wert])) - (SUMX(MeasureTable,[fck])) ,
ALLSELECTED(TestResults[Index],TestResults[Plant])
)

After all calculation I need the Standarddeviation.