This is designed as a fix to the problem of warlocks having too few spell slots.

Pact Magic

Your arcane research and the magic bestowed on you by your patron have given you facility with spells. See Spells Rules for the general rules of spellcasting and the Spells Listing for the warlock spell list.

Cantrips

You know two cantrips of your choice from the warlock spell list. You learn additional warlock cantrips of your choice at 4th and 10th level.

 Spell Slots

The Warlock table shows how many spell slots you have to cast your warlock spells of 1st through 5th level. The table also shows what the level of those slots is; all of your spell slots are the same level. To cast one of your warlock spells of 1st level or higher, you must expend a spell slot. You regain all expended Pact Magic spell slots when you finish a long rest. In addition, you regain one pact slot when one of the following occurs:

• You finish a short rest
• You roll initiative
• You use an action to regain a pact slot. Once you use this action, you can’t do so again until you finish a long rest.

For example, when you are 5th level, you have three 3rd-level spell slots. To cast the 1st-level spell witch bolt, you must spend one of those slots, and you cast it as a 3rd-level spell.

At first level, you have two warlock spell slots. You gain an additional spell slot at 5th, 9th, 11th, 13th, and 17th level. The level of your slots are equal to half your warlock level, rounded up, to a maximum of 5th level. 

Spells Known of 1st Level and Higher

At 1st level, you know two 1st-level spells of your choice from the warlock spell list.

The Spells Known column of the Warlock table shows when you learn more warlock spells of your choice of 1st level and higher. A spell you choose must be of a level no higher than what’s shown in the table’s Slot Level column for your level. When you reach 6th level, for example, you learn a new warlock spell, which can be 1st, 2nd, or 3rd level.

Additionally, when you gain a level in this class, you can choose one of the warlock spells you know and replace it with another spell from the warlock spell list, which also must be of a level for which you have spell slots.

Spellcasting Ability

Charisma is your spellcasting ability for your warlock spells, so you use your Charisma whenever a spell refers to your spellcasting ability. In addition, you use your Charisma modifier when setting the saving throw DC for a warlock spell you cast and when making an attack roll with one.

Spell save DC = 8 + your proficiency bonus + your Charisma modifier

Spell attack modifier = your proficiency bonus + your Charisma modifier

Spellcasting Focus

You can use an arcane focus as a spellcasting focus for your warlock spells.