Terve Eino! 
And welcome to the forum There are several ways to do that. Maybe the easiest is to use orx-no-clear which allows you to draw and keep the previous content visible. That way you only draw one circle.
Or create your own RenderTarget instead (that’s what orx-no-clear does for you behind the scenes).
If you want to draw an animated morphing variable thickness line you could take this different approach, but it’s a bit more convoluted:
I’ll create an easy to use function and post it as a reply later.
ps. Feel free to share an image of what you are trying to create (here in the forum or somewhere else like https://imgur.com/ if you can’t yet share images here): maybe a different approach comes to mind when I see it.
Cheers!