I have been talking to people from the Warzone this last month and I have been using DeepL to do so. However, on Android I have to back out, copy paste, rewrite, no no no no thats horrible. Theres too many god damn UI functions to make this a feasible experience on mobile.
Instead, have a keyboard app that uses the suggestion box to show you your language, but types the translation directly into whatever text box you select. Then you don’t have to do all the jackass jumping around.
I would love to see if but, wearing my Comp. Sci. hat, grammar is not a one to one ratio. Take Russian and Ukrainian for example. They lack the articles that we have in English and some of their words change depending on if you are talking about a male or female. Also some of their words change form depending on if the subject is doing the action or not. A lot of this cannot be determined unless you have the whole sentence.
I am currently learning Russian and Ukrainian right now and some of the grammar is just wild. If you have heard of NP complexity, Natural Language processing falls in that domain. It is not that it cannot be done, but some problems cannot be computed easily.