In the second match the guy was giving you huge openings by reaching around your head like that when he was in your guard, but you rushed too much with the armbar attempt without securing the position. Your attacks from your guard were too "straight on." You brought your legs up no problem, but you had no angle, so everything was loose and he was just able to slip out. I have no idea how you managed to lose mount and just fall over from side control. Work on your base I guess?
What division was this?
"Dominate" is a verb. "Dominant" is an adjective. A fighter can dominate his opponent. If he rules his division, he is considered dominant. Yes, this needed to be explained.