The image quality decreases when the size is reduced, what to do?

Question

Adobe Photoshop

I add a new layer to the canvas image. When its size is reduced, the quality drops sharply. How to deal with it?
The quality seems to drop as you zoom in. And here, in fact, the opposite is true ...
That is. It is required to change the size of a layer/image without changing the concentration of pixels per inch/centimeter

Answer 1

Before doing any manipulations with the image, convert it to a Smart Object (RMB on the layer -> Convert to Smart Object). This will save it from a drop in quality when rescaling.