Those Who Die without the Mormon Gospel

Saved and go to Celestial Kingdom

D&C 137:7; “Thus came the voice of the Lord unto me, saying: All who have died without a knowledge of this gospel, who would have received it if they had been permitted to tarry, shall be heirs of the celestial kingdom of God.”

Unsaved and go to hell

Alma 34:32-33; “For behold, this life is the time for men to prepare to meet God; yea, behold the day of this life is the day for men to perform their labors.33 And now, as I said unto you before, as ye have had so many witnesses, therefore, I beseech of you that ye do not procrastinate the day of your repentance until the end; for after this day of life, which is given us to prepare for eternity, behold, if we do not improve our time while in this life, then cometh the night of darkness wherein there can be no labor performed.”

So which is it?

How can you believe in both books? How can you believe Joseph Smith was a true prophet of God and trust his contradictions?