#1: You don't need the /subjects attribute in the <expt> element. You can delete it.
#2: Your <variables> element assigns different block orders (compatible vs. incompatible first) based on the provided *subject number*. I.e., a participant with an *odd* subject number (1, 3, 5, ...) will receive the compatible blocks first, a participant with an *even* subject number (2, 4, 6, ...) will receive the incompatible blocks first.
If you want the assignment to be done based on the *group number*, you need to specify
<variables>
/ groupassignment = groupnumber/ group = (1 of 2) (block1_bs=targetcompatiblepractice_bs;
block3_bs=compatibletest1_bs;
block4_bs=compatibletestinstructions_bs;
block5_bs=compatibletest2_bs;
block6_bs=targetincompatiblepractice_bs;
block7_bs=incompatibletest1_bs;
block8_bs=incompatibletestinstructions_bs;
block9_bs=incompatibletest2_bs;
block1_Kommunikation=targetcompatiblepractice_Kommunikation;
block3_Kommunikation=compatibletest1_Kommunikation;
block4_Kommunikation=compatibletestinstructions_Kommunikation;
block5_Kommunikation=compatibletest2_Kommunikation;
block6_Kommunikation=targetincompatiblepractice_Kommunikation;
block7_Kommunikation=incompatibletest1_Kommunikation;
block8_Kommunikation=incompatibletestinstructions_Kommunikation;
block9_Kommunikation=incompatibletest2_Kommunikation)
/ group = (2 of 2) (block1_bs=targetincompatiblepractice_bs;
block3_bs=incompatibletest1_bs;
block4_bs=incompatibletestinstructions_bs;
block5_bs=incompatibletest2_bs;
block6_bs=targetcompatiblepractice_bs;
block7_bs=compatibletest1_bs;
block8_bs=compatibletestinstructions_bs;
block9_bs=compatibletest2_bs;
block1_Kommunikation=targetincompatiblepractice_Kommunikation;
block3_Kommunikation=incompatibletest1_Kommunikation;
block4_Kommunikation=incompatibletestinstructions_Kommunikation;
block5_Kommunikation=incompatibletest2_Kommunikation;
block6_Kommunikation=targetcompatiblepractice_Kommunikation;
block7_Kommunikation=compatibletest1_Kommunikation;
block8_Kommunikation=compatibletestinstructions_Kommunikation;
block9_Kommunikation=compatibletest2_Kommunikation)
</variables>
For details on how condition assignment works, see
https://www.millisecond.com/forums/Topic13856.aspx