Using the Attack action, you can make a special melee attack to shove a creature, either to knock it prone or push it away from you. If you’re able to make multiple attacks with the Attack action, this attack replaces one of them.
The target must be no more than one size larger than you and must be within your reach. Instead of making an attack roll, you make a Strength (Athletics) check contested by the target’s Strength (Athletics) or Dexterity (Acrobatics) check (the target chooses the ability to use). If you win the contest, you either knock the target prone or push it 5 feet away from you.
A prone creature’s only movement option is to crawl, unless it stands up and thereby ends the condition.
The creature has disadvantage on attack rolls.
An attack roll against the creature has advantage if the attacker is within 5 feet of the creature. Otherwise, the attack roll has disadvantage.
As it can not move due to grapple reducing its speed to 0 it will have to break grapple first. correct?
Rolls
Dex - Save DC 14 - (1d20+0)
(4) = 4
shove (contested ability/skill check) prone - (1d20+5)
(18) + 5 = 23
paw vs invisible - (hit:1d20+9, dmg:2d6+5)
hit:1d20+9 : (5) + 9 = 14
dmg:2d6+5 : (16) + 5 = 12