Hi Astrapho,
Either you believe the Bible is God's word or you do not. As Paul has 13 Epistles that take up a large portion of the New Testament, you would have to discredit quite a bit. Here is what Peter thought of Paul.
2Pe 3:14 Therefore, beloved, looking forward to these things, be diligent to be found by Him in peace, without spot and blameless;
v. 15 and consider that the longsuffering of our Lord is salvation--
as also our beloved brother Paul, according to the wisdom given to him, has written to you,
v. 16 as also in all his epistles, speaking in them of these things, in which are some things hard to understand, which untaught and unstable people twist to their own destruction, as they do also the rest of the Scriptures.
Now at the Jerusalem Council we see that Paul is among those there as a prominent member/Apostle and it is obvious that he is considered by the rest to be equal with them in the work.
Act 15:6 Now the apostles and elders came together to consider this matter.
Act 15:12 Then all the multitude kept silent and listened to Barnabas and Paul declaring how many miracles and wonders God had worked through them among the Gentiles.
Act 15:22 Then it pleased the apostles and elders, with the whole church, to send chosen men of their own company to Antioch with Paul and Barnabas, namely, Judas who was also named Barsabas, and Silas, leading men among the brethren.
Act 15:25 it seemed good to us, being assembled with one accord, to send chosen men to you with our beloved Barnabas and Paul, v. 26 men who have risked their lives for the name of our Lord Jesus Christ.
So why would we doubt Paul if the rest of the Apostles did not?
after all Jesus founded the rock of his church on Peter, not Paul (Matt 16:18)
Mat 16:18 And1161 I say also2504, 3004 unto thee,4671 That3754 thou4771 art1488
Peter,4074 and2532 upon1909 this5026
rock4073 I will build3618 my3450 church;1577 and2532 the gates4439 of hell86 shall not3756 prevail against2729 it.846
G4074
Πέτρος
Petros; a noun akin to G4073, used as a proper name; “a stone” or “a boulder,” Peter, one of the twelve apostles.
G4073
πέτρα
petra; a prim. word; a (large mass of) rock.
As you can see these are two different words used for rock in that verse, the first is referring to Peter, but the second is referring to Christ Himself. It is Jesus Christ that is the "Cornerstone."
Eph 2:20 having been built on the foundation of the apostles and prophets, Jesus Christ Himself being the chief cornerstone,
There is a Bible study that goes into a lot of detail about 'Do James And Paul Contradict?' This will give you much information on the validity of the work that Paul did as an Apostle.
http://forums.bible-truths.com/index.php/topic,9742.0.htmlmercy, peace and love
Kat