Its been almost a year since I visited the site seforimonline.com last time I saw the site they had a sefer called “sefer HaVikuach” which if memory serves me is the Rambans writings on his famous disputation that got him kicked out of spain. If that’s not what it is, then they have another sefer which is the rambans writings on this disputation and seer havikuach is another sefer written by a different rishon that throughly refutes xtianity and its beliefs as well as its “proofs” from tanach.
In general, there are some fascinating seforim that are available to be learned (and I think downloaded) at that site.