D&D 5E The whip needs love.(updated last time)

[Lehrbuch]

Can you understand it? If you can then what is the issue.

The issue is that your version is still unclear. I think this is a simpler and clearer and cleaner version:

Whip Master
+1 DEX
Gain proficiency with whip.
When you make a successful melee attack with a whip on your turn you may use a bonus action to make another attack upon the target of the successful attack. This bonus attack must be either a Shove attack to knock the creature prone, or a Disarm attack. If using the bonus Shove attack to knock the creature prone, your roll in the contest is an attack roll with the whip (instead of a Strength (Athletics) check).
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[RCanine]

I suppose it would be unhelpful and pedantic to point out that the whip was not actually (with some variations proving very minor exceptions) an instrument used for warfare? At least to the best of my knowledge.

Remember that 5th edition weapons are broadly defined. A whip could as much be a leather bullwhip as a length of chain, an Urumi or Jiujiebian.

As far as the feat goes, I think better than disarm on attack would be some more generic utility:

• As a bonus action you can crack you whip, making a loud noise and giving you advantage on intimidation checks.
• When you hit with a whip, you can choose to grapple the target rather than do damage. While the target is grappled you cannot attack with you whip.
• You can use your whip to manipulate objects within your whip's reach, including using Dexterity (Slight-of-Hand skill checks.
• While wielding a whip you can use the Help Action to aid the attack of an ally against any creature within your whip's reach.
• You gain advantage on Strength (Athletics) checks to jump or climb distances equal to or smaller than your whip's reach if you have something to anchor your whip to.

 

[hejtmane]

A Valor Bard or Bladesinger can take Spell Sniper and use Booming Blade with it.

It is thematic as the whip cracking can be the 'booming' part of it. You can also take Thunderclap, Shatter, etc. for spells.

Because you have reach, the enemy will need to take the extra damage to get to you.

Except that does not work or green-flame blade unless your DM house rules the spells verified by Sage Advice booth spells range is 5 feet from you so reach weapons like whip and polearm do not help on those spells without a house rule

Want to note recently found that spell sniper allows the spell to be moved to 10' sage advice confirmed so with a feet you can leverage the whip range and green flame blade

 

[abirdcall]

Remember that 5th edition weapons are broadly defined. A whip could as much be a leather bullwhip as a length of chain, an Urumi or Jiujiebian.

As far as the feat goes, I think better than disarm on attack would be some more generic utility:

• As a bonus action you can crack you whip, making a loud noise and giving you advantage on intimidation checks.
• When you hit with a whip, you can choose to grapple the target rather than do damage. While the target is grappled you cannot attack with you whip.
• You can use your whip to manipulate objects within your whip's reach, including using Dexterity (Slight-of-Hand skill checks.
• While wielding a whip you can use the Help Action to aid the attack of an ally against any creature within your whip's reach.
• You gain advantage on Strength (Athletics) checks to jump or climb distances equal to or smaller than your whip's reach if you have something to anchor your whip to.

These are mostly things you can do anyway without the feat.

This isn't 3.x.

You don't need an explicit rule to be able to do something.