Going back to the original question(s)
That was explained, the image is single layer, has no alpha channel (transparency) and the background (BG) colour is set to white.
The solution, use more than one layer, the bottom layer is the background, the top layer is where you paint and erase.
This has nothing to do with the eraser tool, it depends on the image and very often it is not easy. Assuming a single layer and a photo/graphic. Various ways.
1. Use the clone tool or heal tool to paint out the part you want removed.
https://docs.gimp.org/2.10/en/gimp-tool-clone.html and https://docs.gimp.org/2.10/en/gimp-tool-heal.html
quick demo of clone tool: https://i.imgur.com/PV9O1Sn.mp4
2. Use a third-party plugin to recreate the missing pixels using the surrounding parts of the image.
Examples:
https://patdavid.net/2012/08/getting-aro...selection/ resynthesizer plugin
https://patdavid.net/2014/02/getting-aro...ware-fill/ gmic plugin
Quote:Just started. I have an image on wich I paint. When I erase it goes through the whole image and becomes white. ...and only one layer
That was explained, the image is single layer, has no alpha channel (transparency) and the background (BG) colour is set to white.
The solution, use more than one layer, the bottom layer is the background, the top layer is where you paint and erase.
Quote:How should I erase something and keep my background intact ? I'm sure its easy, but I can't find.
This has nothing to do with the eraser tool, it depends on the image and very often it is not easy. Assuming a single layer and a photo/graphic. Various ways.
1. Use the clone tool or heal tool to paint out the part you want removed.
https://docs.gimp.org/2.10/en/gimp-tool-clone.html and https://docs.gimp.org/2.10/en/gimp-tool-heal.html
quick demo of clone tool: https://i.imgur.com/PV9O1Sn.mp4
2. Use a third-party plugin to recreate the missing pixels using the surrounding parts of the image.
Examples:
https://patdavid.net/2012/08/getting-aro...selection/ resynthesizer plugin
https://patdavid.net/2014/02/getting-aro...ware-fill/ gmic plugin