How to engage as protoss?

Below is a replay where we're both my Terran opponent and I are at roughly the same level in the game and then he just runs his bio army around my army to my collosus and kills 'em , this basically loses me the game, I'm just curious how I should get up engagements as Protoss. Any help would be appreciated.

I'm a mid silver protoss and this Is one of the many mistakes I make in my game. Feel free to point out anything you 'd think will help me improve my play.