Fusion Transition

hello. i made 2 fusion composition in Edit timline then gone to fusion made some motion graphics. then back to editor to add transition between them. it wont accept the transition. or when i trick it with using a solid color (png format not generated) it accept it but i see a black layer at the end of transition... they not transitioning smoothly ... not even for a simple transition like cross dissolve...

is there any workaround to add transition to your composition in editor?
thanks.

i'm trying to make 2 minute motion graphic on narration... so if you can tell me a good working method on projects like this I'll be grateful.