I’m new here and English isn’t my first language so sorry for any mistakes.
I have an issue with the build in Gerber viewer of Kicad6.
When I export from the viewer to the PCB editor my straight lines becomes oval?
I suspect it’s some kind of bug, as johannespfister also already mentioned.
But I think it also does not matter much.
The concept of a “footprint” does not really exist in Gerber files, and therefore you also can not export footprints to a KiCad PCB. You can export them as copper zones / pads, but in my opinion it’s better to just delete all those pads and replace them with real footprints. Some time ago I made a FAQ article of how to re-create a KiCad project from Gerber files:
Of course, you can already rewrite everything… But usually only gerber and not a project are needed to produce or order boards… In this case, in the normal gerber editor, changing all sites (apertures) from oval to rectangle will take 5-10 minutes
The bug will probably not be fixed in KiCad 6. I even doubt that the current stable version, 7.0.2, has it fixed. If you want the bugfix you can download the the Nightly version (but you can’t open the kicad_pcb files created from KiCad 7 with KiCad 6), download the source and compile it yourself or wait till KiCad version 7.0.3 is released (i have no idea when this will be).
Next time you post a bug or when someone ask about your version, go to: Hilfe → Über KiCad → Kopiere Versionsinfo (no idea how it is named in your language) and post the content of the clipboard. But since you are on KiCad 6, you don’t have this bugfix implemented, no mater which version exactly.