Why does the dog trainer make it look so easy?!

She was following all his commands like a pro. But with me she only does the ones that are convenient.
Sit
Focus
Down
Come
Speak & quiet combo (not separately yet.)

But stay, Wait and leave it - she won’t do - with me that is- she’ll do it with the trainer but not me.

I gotta keep trying 😣😣😣😣