Activate Need for Speed by sacrificing Gruul Turf.
When Gruul Turf dies, Toph, Hardheaded Teach triggers, returning Gruul Turf from your graveyard to the battlefield tapped.
When Gruul Turf enters, it triggers, returning the artifact cast in step 1 from the battlefield to your hand, as it's a land due to Toph, the First Metalbender.
Resolve the Need for Speed ability
Repeat.
This clever engine transforms a simple 0-cost artifact into an endless mechanical loop by leveraging Toph, the First Metalbender to turn your nontoken artifacts into lands. With that foundation set, Need for Speed provides the necessary sacrifice outlet by letting you feed those newly minted land-artifacts for haste, while Toph, Hardheaded Teacher capitalizes on your continuous spell-casting with a steady stream of earthbending triggers. Whenever a land you control hits the graveyard, Toph, Hardheaded Teacher swoops in to resurrect it, and the incoming Gruul Turf conveniently bounces your original artifact right back to your hand to restart the cycle.