What makes you think that those verses mean that Paul preached another gospel?
What do you mean by another Gospel? Paul preached the revelation of Jesus Christ.
Galatians 1:11-12New American Standard Bible (NASB)
11 For I would have you know, brethren, that the gospel which was preached by me is not according to man.
12 For I neither received it from man, nor was I taught it, but I received it through a revelation of Jesus Christ.