There is a lot about the Gospels that Paul forgot to mention. That doesn't invalidate the Gospels.
Neither does it invalidate Paul.
But your comment indicates mind reading on your part or some claim to special knowledge or revelation, that you know that Paul *forgot* to mention stuff.
It would be more accurate to comment that Paul *didn't* mention a lot about the Gospels.
My guess is that likely the reason he didn't rehash what happened in the Gospels was that it was because what was recorded in the Gospels for us, was pretty common knowledge to them, back in the days when Paul wrote his letters.
In the book of Acts, chapter 9, Paul was given a specific message of what he was to preach so there was not a forgetting of the Gospel or any question of invalidating them.
Paul’s commission came directly from Christ as did that of his other apostles so there is no conflict between the message of the Gospels and what Paul preached, it was “all scripture, inspired by God”.