Blending colors to fill in white cut-out lines?

[Pier]

thanks Rich, i was getting super impatient since i spent like 5 hours already on this silly image, so right after posting this i ended up just opening paint 3D and using the 'spraycan' tool to manually fill in the white spaces. It took me an hour but the result is near perfect actually. I really find GIMP so counter-intuitive. Like when you insert a new image you actually have to select the tool to move and resize it, while doing exactly that is the first step for anyone inserting an image onto another you would think. And 'escape' doesn't actually cancel a selection, you have to enter a menu to cancel a simple selection. It's really a shame if you ask me, things could be so much user friendly . Thanks anyway rich, i will save your advice for next time (which will come)