[How to make the black shape transparent or cut the element behind?]

but if it saved in SVG or PDF, the blend erase won't work

[How to make the black shape transparent or cut the element behind?]

the goal:

[How to make the black shape transparent or cut the element behind?]

Hello, how to make the black shape transparent/cut the element behind in Affinity Designer? i've tried geometry operation a  nd blend layer Erase. The blend layer erase works but no when i've save it to svg. It only works on PNG.