Please Answer for me!

Can i achieve the following:
Build an Asterisk Server with one SIP IP phone connected inside and an
outside phone line connected to a standard external modem, so that
Asterisk would be a PSTN gateway for that One phone?

a standard modem wont work, you would want to have a look at look for tdm400 cards, buy one with 1 fxo port.

Then it would work just fine


thank you for answer