Is it true that some of the apostles of Christ never wrote any books of the Bible but just helped with spreading the gospel?
Yes, this is true. While it was part of the abilities of a first century apostle to write Scripture because he spent physical time with Jesus during his 3 1/2 years of ministry on earth, not every Apostle wrote Scripture.
Apostles had great authority in the church because the New Testament had not yet been completed until the end of the first century. The church relied on the leadership and first-hand knowledge of the original apostles to guide them until Scripture was completed.
The apostles would also contribute to the writing of Scripture that others were doing. For instance, John Mark was not an apostle, but much of his information came from contributions by Peter.
The apostles who did write Scripture personally our Matthew, John, Paul, and Peter. We don’t know who wrote Hebrews. James and Jude were physical brothers of Jesus. Luke thoroughly researched the book of Luke and traveled with Paul as he was writing Acts.
All of the other apostles were actively involved in ministry of all sorts from preaching to evangelism to prophecy within the church. They founded new works all over the world.