FAST UI blur on mobile

Hello!

I am using Unity 2019.4 with built in pipeline and want to blur the whole image when I open my pause dialog.

I have already bought 2 assets on the Unity store but none of them was fast enough. One asset caused a performance hit when I activated the effect for the first time. I checked the implemenation and the script used method void

Code (CSharp):

1. void OnRenderImage(RenderTexture src, RenderTexture dst)

with 4 Graphics.Blit() calls.
I found some threads that mentioned using Graphics.Blit() and OnRenderImage() is slow and its better to use OnPreRender and OnPostRender

Unfortunately my shader and unity render knowlodge is limited. Does anyknow have an idea how to implement a FAST blur for mobile devices? Or at least knows an asset that works? (After wasting 20€ I don't want to waste more money...)

Thanks!