Nice response! He's right! if you haven't done much ab training starting off with function movements that use the abs as a stabilizer is the best start. I would also alternate mount climbers and T-raises, also dumbbell swings are good

Doing isolation exercises on your abs should only be done after you've adapted to all the basic body weight excises. Stabilizing exercises are your key for nice abs. Hope this helps!

To your success,

Travis