Welcome to JWC Daniel.
Your questions and discussion are also most welcome.
All of us would like to be of any assistance we can in such a life changing decision.
From a (SBNR or Spiritual But Not Religious) believer's perspective if you would like to develop faith and spirituality, religion is not the way to go. Religion and spirituality are antithetical or opposite.
Finding a believer to talk to who has the gospel message in their heart and on their lips is the way to go.
I would start with the gospel according to Paul, and especially starting with the book of Romans.
Religion is a bad road to go down. And the Watchtower is one of the worst religions of the lot. The Watchtower has deception down to a fine art. The Watchtower is 500 years behind the Catholic Church in terms of mending their ways, especially in the area of incest and pedophilia.
A life in the Watchtower always ends badly. Please do not even consider it.
In essence the Watchtower will lead you onto the wrong playing fields: doctrinal ethnocentrism, legalism, moralism and Gnosticism (PM me if you'd like me to unpack these).
The playing field where the real game is on is the unabridged gospel message.
And it would be wrong to get your girlfriend and her family's hopes up that you might be interested and join their religion.
That having been said you and and your girlfriend could potentially benefit from privately making a study of the gospel or "Good News" in the electronic Watchtower library. I'd be happy to provide a 1-page summary/map/framework. What you will find in print differs markedly from what is allowed to be taught, discussed and believed. The Watchtower and their hierarchy are rabidly hostile to the gospel or "Good News" but will deny it. Their deception is easy to spot if one is very intimate with the full gospel.
The issue is largely about control over others. Specifically clericalism, sectarianism, denominationalism, magisterium and hierarchy. All things that the gospel directly challenges. (Once again PM me if you'd like me to unpack these).
Best wishes
Fernando
SEQ, Australia