Opacity problem with picture layer with mixing negative

I noticed a problem with the mixing negative function in Adobe Express. When you save as in preview the opacity mix is not rendered correctly into the final picture. I'm attaching pictures of the process.

First: the process

Second: the look in Express

Third: final result

I want to add that it would be great when there would be a function to select the layer you want to edit for when a layer is bigger than the actual frame you have to move to get to the layers below.