Modifying different objects in photo - Affinity Photo V2

Hi all,

I am a beginner photographer, and start to play with Affinity Photo. I know how to use basic tools (curves, exposure, filters) and I am starting to play with masks.

I have a portrait photo, for which I would like to do two different operations:

• Desaturate the background
• Sharpen a bit the person on the foreground.

For example, if you consider this stock photo:

I would like to desaturate slightly the yellow background and sharpen the person.

I have tried playing with various masks, but I don’t manage to obtain the effect I want. I either manage to desaturate the background and sharpen everywhere, or to sharpen the person and desaturate everywhere.

I am a bit at lost at what to search for to find adequate content. Does anyone have a link towards some guide or give me a quick idea of what I should use?

Thanks!