Galatians 1:8-9
8 But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.
9 As we said before, so say I now again, if any man preach any other gospel unto you than that ye have received, let him be accursed.
You notice that you deliberately dropped the words that I have bolded, and thus came to a different interpretation?
It wasn't an exact quote, but it does not change the interpretation.
Paul is actually saying if the gentiles are preached another gospel other than the one what they are receiving from Paul, let the preacher be accused.
Your interpretation is not consistent with other scripture. Look at Romans 1
16 For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth; to the Jew first, and also to the Greek.
Look at Romans 1:
9 That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.
Notice 'gospel' in the singular, is the power of God unto salvation to the Jew first, and also to the Greek.
See also Romans 10
10 For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.
11 For the scripture saith, Whosoever believeth on him shall not be ashamed.
12 For there is no difference between the
Jew and the Greek: for the same Lord over all is rich unto all that call upon him.
How does this Gospel that Paul preached change between Jew and Gentile?
I Corinthians 15
15 Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand;
2 By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain.
3 For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;
4 And that he was buried, and that he rose again the third day according to the scriptures:
Whether you are Jew or Gentile, Christ died for our sins, according to the scriptures. He was buried, and He rose again the third day.