Case Statement (Tableau) to DAX

damjanv123 , You can try like

Switch([age_group]
, "AgeGRoup_0-4" , 0.062
, "AgeGroup_5-9" , 0.065
, "AgegRoup_10-14" , 0.059
, "AgegRoup_15-19" , 0.060
, "AgegRoup_20-24" , 0.065
, "AgegRoup_25-29" , 0.070
, "AgegRoup_30-34" , 0.072
, "AgegRoup_35-39" , 0.067
, "AgegRoup_40-44" , 0.067
, "AgegRoup_45-49" , 0.066
, "AgegRoup_50-54" , 0.065
, "AgegRoup_55-59" , 0.063
, "AgegRoup_60-64" , 0.056
, "AgegRoup_65-69" , 0.051
, "AgegRoup_70+" , 0.112
)

Switch(true()
, [age_group] ="AgeGRoup_0-4" , 0.062
, [age_group] ="AgeGroup_5-9" , 0.065
, [age_group] ="AgegRoup_10-14" , 0.059
, [age_group] ="AgegRoup_15-19" , 0.060
, [age_group] ="AgegRoup_20-24" , 0.065
, [age_group] ="AgegRoup_25-29" , 0.070
, [age_group] ="AgegRoup_30-34" , 0.072
, [age_group] ="AgegRoup_35-39" , 0.067
, [age_group] ="AgegRoup_40-44" , 0.067
, [age_group] ="AgegRoup_45-49" , 0.066
, [age_group] ="AgegRoup_50-54" , 0.065
, [age_group] ="AgegRoup_55-59" , 0.063
, [age_group] ="AgegRoup_60-64" , 0.056
, [age_group] ="AgegRoup_65-69" , 0.051
, [age_group] ="AgegRoup_70+" , 0.112
)

Also, refer

SEGMENTATION

https://www.daxpatterns.com/dynamic-segmentation/
https://www.daxpatterns.com/static-segmentation/
https://www.poweredsolutions.co/2020/01/11/dax-vs-power-query-static-segmentation-in-power-bi-dax-power-query/
https://radacad.com/grouping-and-binning-step-towards-better-data-visualization