While I would not say we Christians “nicked” most of our religion from pagans, i would say that many of our traditions include pagan origin. For instance Easter and Christmas are at the same time as the tradition pagan holidays of Eastre and Yule (hope I got the names right).
Also many of our beliefs about hell can be traced to Persian and Greek roots, as well as Egyptian and Zorostranism (im sure I butchered that).
And certainly much of the old testament, especially Genesis has commonalities with other sacred creation stories.
However, to imply that Christianity is without its own origins would not be a correct statement, while the expressions may be derived from other cultures, the motivation for such expression stems from Christ.
I would also tend to disagree with saying true Christians get all they believe from the Bible. For one thing, this means many around the world without access to Bibles are not “true” Christians, which I feel is a categorically untrue statement. It also means that those Christians living prior to the creation of the Bible were not true Christians, and I do not think many would wish to claim that of the Apostles and other disciples of Christ.
We are served neither by denying the Bible or by denying the roots of our traditions.