Q. 1. In my city, the only Churches that offers Bible studies are the Protestant Churches. To learn about the teachings of Jesus, I have joined one of those groups. Someone in my parish told me that it is a sin to attend non-Catholic Bible studies? Is that true?
A. 1. To attend a Protestant Bible Study is no different than reading a Protestant book. In both situations, you have to remember that the teachings of Jesus that you are learning are those according to the Church that is presenting them. For example, the Anglicans will give you an Anglican interpretation; the Lutherans will give you a Lutheran interpretation, etc...
The Protestant Churches do not agree with the Catholic teachings on the matter of the Keys to the Kingdom of Heaven [Matthew 16] or the permanent Real Presence of Jesus in the Eucharist. [John 6] Their interpretation can lead you away from the truth and even cause you to lose your faith in the Catholic Church. If such occurs, then attending non-Catholic Bible Studies was a sin because you did not defend the One, Holy, Catholic and Apostolic Church as you were called to do during the Sacrament of Confirmation.
Finally, the Catholic Churches do offer Bible Studies on a weekly basis. Those studies are in a different format than those presented by the Protestant. Every Sunday, when you go to Mass and listen to the homily of the Priest who is explaining the Bible readings of the day, you are then taking part in a Bible study. By listening to the Word of God, you are growing in Biblical knowledge, understanding and wisdom.