Hey, @gianni_alessi. Welcome to the Lightroom Community. I'll help you figure this out.
You can use Photoshop on the desktop for pixel-based editing. In Lightroom, you can use Lens Blur to blur parts of your image: https://adobe.ly/4gjJPYw
Let me know how it goes. Thanks!
Sameer K
(Type '@' and type my name to mention me when you reply)