You must be in fellowship prior to your Bible study, so that the spiritual information you receive can become a source, of blessing to your soul and produce spiritual growth.
20 Now [de] the things which [hos] I write [grapho] unto you, [humin] behold, [idou] before [enopion] God, [theos][hoti] I lie [pseudomai] not. [ou] KJV-Interlinear
20 (Now in
what I am writing to you, I assure you before God that I am not lying.) NASB
Paul is writing to the Galatians, because they have fallen away from the true gospel, and had turned to various forms of salvation by works gospels, all of which were false.
Paul had already visited the region and those people responded to the true gospel of faith, or salvation by faith and had thrived considerably as a result.
But Paul left to go to other places, and that is when evil people came in and began teaching false doctrines.
Now this is not mentioned anywhere, but Paul is addressing the truthfulness of his message and the means of his instruction, which indicates that this background has been questioned, most likely by those who were teaching the false doctrines, and as such, attacked Pauls character as well.
Therefore, Paul addresses his history and background in this first chapter.
He restates the story of his salvation, the story of his instruction by no man or institution, and the brief meeting with Peter and James.
And this defense of his character and history should not have been necessary, had his truthfulness not been questioned. So, he states that this is the true nature of himself and not something else.
He did not spend time in Jerusalem learning. He did not receive instruction from the apostles. And, he makes those facts clear by means of his own statements and writing, which would necessarily cancel anything and everything that others might have said or implied.
When Paul was not around, all that people could go by was the general gossip that was offered, with no one there to correct or contradict it. And that teaches us a spiritual lesson here.
When people lack truth in their souls, then they will have a tendency to listen to and accept gossip without questioning the source.
The gossip is wrong, but then, the listener who accepts it, is wrong too. Only truth assimilated in the soul can discern between the truth and idol talk. When truth is lacking in the soul, then people will leap at repetitive false talk without hesitation.