Is it permissible for one to “celebrate Christmas” as in decorating the house, having a christmas tree, getting each other gifts, and even visiting Churches with their Christian friends as a form of showing some respect for their friend’s religious beliefs?

There’s no harm in decorating the house or giving each other gifts. A Christmas tree could be problematic as it is the tree was imported from Paganism who used to worship the tree. Therefore should be avoided.

Visiting the churches is also allowed.