When saving image, almost all is white despite of what is on the scree

[rich2005]

Difficult to say from your screenshot but a couple of possibilities.

Exporting to tiff - disable the layers option. That gives a multi-page file and all you see is the 'first page' .

   

There is a floating selection, irrespective of the outcome you need to either anchor it or promote to a new layer.

   

(Just a comment, text looks small for OCR-ing and if using tesseract then formatting will be an issue, but that is another story)