Beowulf comes from the Anglo Saxon tribes who invaded Britain and were bound by certain codes of conduct. These were older pagan values of personal honor codes and blood vengeance. However, Christian values were also present in old English literature and these can be seen in Beowulf too. Essentially Beowulf is a story of pagan warriors based on true events (Hygelac's battle for example occurred inaround 520 AD). As the tale began it would have been an oral tradition passed by storytellers at camp fires, but as time passed christian values were added.
The general opinon from historians is that the oral tale was collated sometime in the eighth century, probably by one writer, and this was after England had become Christian but pagan habits still were strongly imbedded within the culture.
It is debatable whether one of the values represented by Beowulf is a faith in God or a faith in fate. Look at lines 662-702 in which Beowulf places trust in God - the language is Christian , but does he trust strength first and God second?