Enough-Best or Too Much-Too Bad?

i am 16, first of all, and in a dilemma. could i, on the same day, do tempo in the morning and speed work in the afternoon (some 12 hrs distant from each other). maybe 3 times a week and once only speed and the others passive rest or something like that. basically i want to get an ida if that could be done without me destroying myself. all of this being in season.

i don’t do weights cause of back problems and stuff and i wat to wait a year or so before i do weights and destroy my back because in 1 year time i’ll be naturaly stronger etc.

so i would like to know if i can opt to a lot of tempo and speed work without killing myself.