TriumphFriend

Or even easier still, just select the Blur Brush Tool and blur those faces into oblivion.
Assuming you never want to see (recover) them again then the job's done.

Hi @TriumphFriend,
The easiest way would be to duplicate your layer, Apply blur on the new layer created, and use a clipping mask to "mask" the areas you need. 
Thanks,
Gabe. 

Hello
 
I am a newbee with affinity and looks for some hints about photo manipulations. 
 
I wish to change a photo from color to black and white but only in a special area. 
 
I have a center motif, that should be coloured, the rest should be in black and white only. 
 
Are there some hints, how can I easy do this. 
 
Perhaps there is any video tutorial...
 
Regards
Thomas
 
 

Now there are 28 Tutorials in german. I trie to explain as short as possible because I dont want to steel your precious time.
 PastorPixel Affinity Photo german
Specially for Beginners, you can start at the beginning with Basics
There are some Videos about Color Correction, Gradiation, Histogram etc. Tonwertkorrektur
Then you will find 2 Videos with Masks and  Cutting out Hair
Layer Basics, Brushes Basic, the nice Panorama feature and many more. I hope you will enjoy it.

Hi
I have made 12 new  Affinity Photo Tips in german
I hope you enjoy it. I am planning to make more.