Welcome to Ireland Reaching Out!
I've been to Galway city a number of times and are familiar with two churches. There is the Cathedral of Our Lady Assumed into Heaven and St. Nicholas. This beautiful church built I believe in the 1960s right near the River Corrib. There is also an Augustinian church on Middle Street closer to the Spanish Arch. See links below. Not sure how the 19th century parishes evolved into these churches.
In addition, these links provide info on other parishes in the city and surrounding area.