quoting seraphinak, Disinterest:

It is the closest thing to an accent over the o that my phone has. Even the Spanish keyboard doesn't have proper accent marks ?

Well, in that case, how about using a computer, or a laptop? Like, seriously. It has way better capabilities regarding input than a phone, even though it's certainly astonishing how powerful phones have become over the last 5–10 years. But there's some things that computers are still better at, e.g. writing more complex things than a WhatsApp message.

You may also be interested in Annie's dictionary-keeping capabilities. Also, this and this very basic introduction to how some important parts of languages work and how to leverage knowledge about how real-world languages work to make fictional ones.