@Phoenix3000
This type of radar, the FUMO 29, will mount itself correctly only on:
Type VIIB turm 1 and 2
Type VIIC turm 1
Type IXB turm1
Type IXC turm1
I'm guessing that on the picture is type VIIC/41 (that is turm 3 for VII).
You should pass installing that radar and choose the next one (if available).