Getting silhouette made for this isn’t to difficult but it will require either adding some vector lines and joining nodes and breaking nodes, or using some shapes and do some unions or differences.
Look at the bottom grass where the couple is standing. You would need to break a node and take a line and join it to a line on the base of the tree.
Did you scan the drawing and put it into a vector editing program? If you post that vector, I’ll have ago at it. Otherwise if you take another shot of the card/drawing that doesn’t have any shadows and is a bit flatter, I think I can trace an outline of it for you and do some of the connecting.
I certainly appreciate the difficulty of thinking through this puzzle and using the design tools to join what needs to be joined. Here is something I did that I had to think through to make sure things didn’t drop out.