if u have painted something black u have to set
my.overlay = on;
then the black pixels should be invisible. check out "d3d_autotransparency" in the gamestudio-help (f1). with this variable u can handle that the color of the pixel in the upper-left-edge is used for the overlay (=1) or that black is overlaycolor (=0)
sry but i can't solve your first problem!
ahhh and by the way, the pictures are called "sprites"