Kia ora e hoa ma!
One of the best things we can do to improve our reo is increasing our exposure to it. Reading is one of those things, especially if you can get your hands on some really old texts. I've found a letter from 1885 regarding William Colenso's mission to write a book, a compilation of as many Maori words as possible. You can find the text here:
https://paperspast.natlib.govt.nz/books/ALMA1885-9919185082802836-E-hoa---Tena-ra-ko-koe--Tena-pea
You can find his book here. Unfortunately he died before he could complete it:
https://books.google.co.uk/books?id=QfkUAAAAYAAJ&printsec=frontcover#v=onepage&q&f=false
Kia ora ra e te iwi! I have a Patreon where I hope to add some additional value. If you'd like the kaupapa, and you appreciate this mahi, you can give a koha here:
A Maori Podcast