It is a very common amongst Muslim learners of Arabic to have his or her goal as the ability to have access to the original texts of Islam i.e. The Holy Qur’an and the Noble Hadith of the Prophet Muhammad (May the blessings and peace of Allah be upon him).
The first thing to say is that the grammar underpinning these two scripts is virtually the same as the grammar underpinning the modern Arabic language taught in the Gateway to Arabic series. The difference is that the deep meaning of the Qur’an texts, as well as the divine construction of it, makes it pregnant with subtleties and implications. Anybody who thoroughly learns and understands the structure of the Arabic language (i.e. the grammar) and learns sufficient vocabulary will have the ability to understand the obvious meaning of the Qur’anic verses as well as the Noble Hadith. However, this is not necessarily sufficient to have a scholarly understanding of those two texts, as this is a lifelong journey!
I must emphasise that the learning of any language is an accumulative skill which takes time to develop. If you thoroughly learn the grammar and vocabulary contained within the Gateway to Arabic course, there is no reason why you should not be able to start establishing a good understanding of the religious texts, as this series will “open the door” for you to interact with Arabic of any description effectively.