Overlap image texture on a material I'm trying to understand nodes, I have this complex material with PBS images textures combined  by color dodge mixer node with a gradient texture for paint it half white and half aqua green.
First I want know if this is the good way to do that.

Then I wanna add an overlay texture (made with photoshop and graphic tablet) to add some details:

So I've tried with mix shader:

On the viewport shading It's seems working (even if it's lighter):

On cycles' preview seems the material is letting pass light trough, in some areas, and the texture is almost invisible:

I've tried also by using one single principle BDSF by adding a mix node but the texture is already almost invisible (I've tried different type of mix without any success)
You're currently telling Blender that there's transparency behind your image, but after that it is mixed with a Mix Shader that is a 50/50% mix between your wall background and your image. In order to put your image over the wall you need to plug the Alpha output of your image into the Factor socket of the Mix Shader, not into the Alpha socket of the Principled BSDF, so basically, if I simplify, it should look like that: