Hi,
You’ll need to make sure that you’ve properly setup smoothing groups for your mesh to avoid this error message.
I don’t use Blender personally so I’m not entirely sure how to setup smoothing groups but this tutorial from a Google search should help.
And to set up the texture for the leaves you’ll need to make sure that you’ve imported the texture > Made a new Material with your material > make sure to use the Opacity Mask to only show the leaves portion of the texture.
Thank you!