🏐Volleyball in All Cities

I've been playing volleyball for a year in our office team in Kolkata. I'm 5'10" and can jump reasonably high but my spikes always get blocked or go into the net. I think my timing and approach are off. I swing too early and the ball is never at the right height when I contact it. Any drills or tips to improve spiking? I practice twice a week at a local court.