For the low notes, you will need to develop power in your 'chest voice'.

The trick to get a good extended range is to 'paste over the joins' - you have to be able to move smoothly and reliably between all 3 'voices' (normally you should have some overlap). As I said, I would recommend getting some compeent assistance. If you try to force any one part of your vocal range too far, can can do damage.

And then, of course, the 4th 'voice' is falsetto, but that has a different tone.

And then there is yodelling...

:-)

So much for most of the Traditional 'Western Styles' of vocal production...

Then there are many others...