Is it true that Christianity endorsed Hermeticism at the beginning?
I am going to guess that you saw someone somewhere claim that Christianity borrowed its belief system in part from Hermeticism. The simple answer to your question is a hard no. No, Christianity never has endorsed Hermeticism and especially primitive Christianity certainly did not endorse Hermeticism. The idea that the apostles learned from Hermeticism is completely false, of course, as Christianity predates the founder of the philosophy.
But this is a bit of an overstatement. Hermeticism is a school of mystical philosophy which grew up in opposition to Platonic philosophy, especially in Alexandria in Egypt, in the first century AD. It was founded by Hermes Trisegistus, who supposedly wrote the most important early documents of Hermeticism. Hermeticism proposes that there is a single idea that connects the heavens to mankind and which pervades all world religions. Hermeticism is monotheistic, proposing a non-interacting deistic kind of God. Some Christian mystics have been attracted to Hermeticism, especially in the time of the Renaissance. Thinkers from Ralph Waldo Emerson to Isaac Newton to Giordano Bruno (who was a neoplatonist, by the way), have mentioned taking ideas from Hermeticism. Also, the practical side of Hermeticism was found useful by the early scientists.
However, the mainstream of Christianity has never been significantly influenced by Hermeticism, and it certainly is not true that Christianity as a whole ever endorsed Hermeticism. In fact, I believe it is safe to say that only a very tiny minority of Christians at any point in history even knew what Hermeticism was, never mind endorsing this rather obscure philosophical/mystical school. If someone told you differently, you should seriously question that person!