Hi,
I'm new to Inkscape and what I'm trying to achieve is make designs from my own photos to papercut in different colors, etc. Something like stencils.
I'm working on a photo of a leopard in a tree and removed what I didn't want from the background (watching some tutorials) but when I apply "Trace Bitmap" it does it as nothing has change, meaning that the whole background is also trace. How can I fix this?
Thank you very much.

Yes, Trace Bitmap works on the raw bitmap image, minus any filters, masks, ... applied to the image.

For the already existing leopard image, you can do the following:

'Make a bitmap copy' of your edited leopard image: Menu: Edit > Make a Bitmap Copy (or Alt+B) - if the result isn't detailed enough, you can set the resolution for the bitmap copy in the settings: Edit > Preferences > Bitmaps: Create : set a higher resolution value here. Trace the copy.

For future images, it might make sense to prepare them for tracing in a different program, i.e. a program that is designed for editing raster images, like the free and open source Gimp (that is: a photo editor).