In Illustrator, you can erase parts of an image with the eraser. To erase a part of an image, first, select it with the marquee selection tool (M), then use the arrow keys to move the selection around. Finally, use the Delete key to erase the entire selection.
There are a few reasons why your eraser tool may not be working. One reason is that it may have been lost or forgotten. Another reason is that the eraser head may have been damaged. If this is the case, you will need to take it to a professional to get it fixed.
In Illustrator, you can use the Edit menu to change the size, opacity, and color of an image.