Only some things hard to understand, not all things.
And we should notice why some of those teachings are hard to understand - the ignorant and unstable twist to their own destruction, as they do the other Scriptures.
The remedy is to rely upon the Holy Spirit, to study so we are not ignorant of God's word and to be single-minded - instead of double-minded - which would make us stable in all our ways. By following these guidelines, we can then understand the teachings God has revealed to us in Scripture. Contrary to some people's ideas, the Bible is NOT a code book requiring an infallible interpreter to tell us what God wants us to know. Those who have the Holy Spirit within are able to learn and understand even the deepest things of the knowledge written in the Bible. It is "foolishness" to those without the Spirit, but we HAVE been given the Spirit to illuminate the truths of God within our hearts.