Peter thought that everything Paul wrote was Scripture: 2 Peter 3:15-16
He refers to Pauls letters then says the other scriptures, directly implying that Paul's letters are Scripture. And since all Scripture is inspired, or God breathed, Paul's letters are inspired, and Paul wrote them in Greek. (or Grrrrrrrreeeeeeeeeekkkk, as you say)
And count the patience of our Lord as salvation, just as our beloved brother Paul also wrote to you according to the wisdom given him, as he does in all his letters when he speaks in them of these matters. There are some things in them that are hard to understand, which the ignorant and unstable twist to their own destruction, as they do the other Scriptures.