I thought the help ui is native Android, but since history says you implemented your own, I have a suggestion to improve it by adding the always-visible search field, or at least an item to quickly call it.
Currently many actions required to perform a search for a custom word in help viewer: I have to make a long tap on a random word in it, then from hamburger menu select the Find item, then remove this random word from search input field and enter my custom one.