I don't succeed to download an image to 300 DPI

[rich2005]

@ Paul

Please have a look at this little (1 and a bit minute) video https://youtu.be/ay2tw5S1S8E

What it shows:
Open jpeg image, and add transparency, cut area.
Check resolution in Image -> Image Properties
Change resolution Image -> Print Size
Have a look at Image properties again.
Export as a png to keep the transparency
close and reopen and check properties again.

The question is, what do you do that is essentially different ?