I'm quite new with Illustrator and I have an issue that I'm trying to find a soluting for a few hours now!

So when I use dark colors on any shape a white thin line appears around it. I tried adding a stroke but the white line moves around the stroke. This is only happening when I'm using dark colors, the lighter colors look as they should! I tried to export as a .png & .pdf and the lines are still visible.

Without a stroke:

With a stroke:

Random light colors:

English is not my first language, I hope I was understood!