A Portuguese partner is not enough.
You have to talk, but you also have to listen a lot, read a lot and write once a while. I have some material that may help you. If you want you can contact me.
If you do not study Portuguese reading a Portuguese grammar for Portuguese, you will never speak correctly.
Books for foreigners try to simplify too much so that they do not frustrate learners because the objective is only to
earn money. They do not go deep and they give rules that only apply 80% of the times.
Do not believe in any grammar written for foreigners.