What is pitch related to in terms of sound? Does it affect the speed? If so, how?

Pitch is the impression the listener gets of the frequency of the sound.

The speed of the sound is not related to its pitch/frequency.

If the speed and frequency were related, that would be a real problem. Bands, orchestras, and choirs could not exist! All the instruments in the orchestra could play a note together, at the same time. But then the higher instruments ... the flute, trumpet, violins, high guitar strings and high piano keys ... would travel to you fast, and the lower instruments ... the trombone, tuba, double bass, bass drum, low guitar strings and the low piano keys ... would travel to you slow. They all played the note at the same time, but by the time you heard it, it would be all smeared out ... every instrument arriving at your ear at a different time!