Dual monitor usage of Acer Aspire 3610: laptop screen turns off

[Juanjavier <juanjavier@ya.com>]

If I plug a second monitor to the laptop VGA out, then laptop
screen turns off, while the second monitor works perfectly.

So I would like to know about a workaround for these two situations:

Screen 2 displays *exactly* the same signal than screen 1 -the laptop one.

Screen 2 displays *an extension* of the image shown in screen 1
(i.e., the mouse pointer leaves screen 1 and re-appears in screen 2)

I use Debian Testing in this laptop, which is an Acer Aspire 3610.

What direction should I take in order to search for information on this?

Regards,

Juanjavier Martínez.