I too lost a friend when I was younger. Its hurts to this day and its been 5 years.
I can relate to the feelings in this poem. well written.

That nothing in this world actually last

last should be "lasts"

But all there is a beat, =
all there is, is a beat. But you could reword it to, but all I hear is the beat.

I think this poem would be better with some punctuation to space the poem out. The wording itself is fine, and the story is very touching. Many will be able to relate to this, and the loss and longing for that someone. You have worded the grief well, and we can sense the dedication in your writing to that someone.

Good work.

A sad yet lovely dedication.