Putting enchatnted bows together and one disappears with the enchantments

I had two enchanted bows, one has Unbreaking III, Flame I, Infinity I and Power V , the other one had Mending I and unbreaking III, I tried to combine both of the bows in te anvil with level 35 and it seemed to work, but then I looked to see the enchantments in the bow and there was only Unbreaking III, Flame I, Infinity I and Power V, the mending had disappeared as well as the bow that was enchanted with it. Now I tried to combine my bow with another one with Mending I and Unbreaking III and it says it's too expensive. I can't combine both bows correctly.