[Export selection to file]

Hello,

I'm pretty new to Affinty and I already stuggle at exporting just a selection in Photo or my SVG without the whitespace around in Designer.

For example I have a red circle on a white background. Now I select the red circle and want to export it without the white background. How can I do that in Affinity Photo?
Simular problem with Affinity Designer. I created a small logo, just text, in the middle of my document, because I didn't know how big it will go and want to export it to an SVG. But now I have giant whitespace around my logo. How do I export it "whitespace less"?

Thank you for your help :)