Eraser tool doesn't erase the lines but turns it white

Thank you guys for your help and suggestions! It turned out to be something really stupid. I didn't add the blue tiles as one fill under the drawing. I realized that I added the tiles fills with the magic wand inside the black lines and below the black lines there is (naturally) no bathroom fill.

You have your answer - you are either on the background layer as Martin_Bns says, or you have a layer turned on underneath that is white and is blocking you from seeing the transparency. Please choose a correct answer .

Hi there, i'ts 99% because your background color is white and you are working on the background layer.
When ereasing, Photoshop shows the background color on the locked layer.

Cheers bro,
Martin

I assume that you expect the eraser tool to really erase the lines as if they were removed from their background, so they become the same blue color as the background? That's not what this tool is supposed to do. You need to use the clone and healing tools for that.

Consider avoiding the Eraser tool when an editable and nondestructive mask or Blend If can do the job.

For Blend If: place a blank layer below the image.

Return to the image layer and double click to bring up Layer Style

In the Blend If section, slowly move the top right slider gently to the left

Turn off the underlying layer - it should be transparent now where you have used the eraser.

The eraser tool deletes pixels on any layer other than a background layer. When used on a background layer it paints with the background colour.

Dave

Can you show a screen shot with your layer panel showing? It looks like your black lines are on the same layer as your background, so when using the eraser took, you will get whatever color you background color is, most likely white in your case.