Shape builder tool, Delete area...

[Jays]

When delete button is selected, and deleting result weired.

1. Example in Affinity

2. Example in Adobe Illustrator

Shape builder.afdesign

[SrPx]

I don't know if "Combine curves" (with the regular move-cursor tool, right click over the whole thing, all curves selected, then Geometry, then combine curves), previous to using shape builder, would help for what you want...I made a video. But I am using the beta 1670, not the official 2.0. 

 

 

 

[SrPx]

Actually...

You might get more what you want if you  :

- Select all, right click, Geometry, Divide (generates the intersection points, it seems Illustrator does this "on the fly"). As the way your original file is, it's long lines with no intersections.

- Then, right click again, Geometry, Combine.

- Use shapebuilder. 

I don't think you always need to do this, just for this case and elements.

 

 

[SrPx]

Or, for this special case, and also using the shape builder tool, you might just use alt+click to eliminate the internal borders that you don't want (without doing the geometry divide + geometry combine). 

[SrPx]

Video with the alt click thing. It is not dragging, but dry clicks. Don't click when highlights an entire shape or then you delete a lot more: