How to get eraserproof layer background?

[gnuimpcub]

Hi,

I am using Gimp 2.8.18 on Debian 9 64-bit Gnome 3.22.2.

My problem: I load a JPG image, add a new layer (fill type: white), paint on the layer, but when I erase some paintstrokes I always erase also the white layer background getting regions of checkerboard pattern.

How can I add a layer I can erase on without damaging the background?

Thanks,

gnuimpcub