Galatians 1:6-7

I am astonished that you are so quickly deserting the one who called you by the grace of Christ and are turning to a different gospel—

(v6, NIV)

Oh my goodness. Those at the church in Galatia are turning to another gospel. They had been preached the gospel of Jesus, but now they are leaving that to follow something else. It is astonishing to Paul and it should be astonishing to all of us. Jesus' gospel is far superior to anything else anyone can even think to make-up or imagine. Why would you throw away what you have been told of about Jesus for anything else? It's like someone for their entire life being used to drinking dirty muddy water from a nearby pond. One day, they are offered clean drinking water free of charge. However, even though the clean water is free, they simply go back to drinking their dirty water or another inferior type of water that has been offered to them. All others pale in comparison.

which is really no gospel at all. Evidently some people are throwing you into confusion and are trying to pervert the gospel of Christ.

(v7, NIV)

These other gospels aren't even worthy to be called gospel. Anything other than Jesus' gospel is nothing. However, these people are being deceived somehow. One method in which they use is to pervert the gospel of Christ. In the ESV translation, it says "distort". These deceivers convince others about a gospel similar to the gospel of Christ, but not the same. The gospel of Christ has been distorted into something that is NOT the gospel of Christ. It is similar, but not the same. If it is not the same, it is really no gospel at all.