Android PShape and Draw Order

Hello

in my processing/android app I use P2D and a lot of PShapes. but the thing is that it seems to me impossible to draw anything other than a PShape UNDER those PShapes I made.

I need to draw lines (complicated/dynamic/cannot do with PShape) in the background but wherever in the code I draw my lines, there appear OVER the PShapes.

Any Idea on how to control this kind of z buzzer for 2D ?

cheers :)

(writing this after a good, long, research on google, forums for v1, 2 and 3 of processing, OpenProcessing etc...)