Resizing the layer and mask together doesn’t always work — actually, if you use the marquee tool first, draw a box with it, and then right click and select free transform, they will resize independently which generally isn’t what you want. To keep them in sync, select the marquee tool, but don’t draw a box first, just right click on the image you want to resize, then select the free transform tool. This will bring up a box with handles, and resizing the box should keep the image and mask together.
Great Design Books
How to Revised and Expanded Edition
A portfolio of inspiration, with insights to further your own design journey.
Draplin Design Co.: Pretty Much Everything
An exquisite book, full of inspiration from one of today's top designers.
Affinity Designer Workbook
A useful, comprehensive, and stunningly beautiful overview of the robust set of tools and features available in Affinity Designer.