Best opening against d4.

I don't do well against d4 generally so can someone recommend some for me

king's Indian or queens indian

U should study the lines and theory. I also recommend doing the lessons

There is no "Best". Merely a finite number of sound openings, namely 8 of them. You have to put in some serious studying at a board, not just playing blitz games.

Those 8 options are, in no particular order:

1) Queens Gambit Accepted

2) Queens Gambit Declined

3) Slav Defense

4) Semi-Slav Defense

5) Nimzo-Indian Defense (Paired with QID or QGD)

6) Grunfeld Defense

7) Kings Indian Defense

8) e6-Dutch Defenses (Classical and Stonewall)

Everything else is either dubious (Chigorin Defense, Leningrad Dutch, Modern Defense) or outright bad (Englund Gambit, Albin-Countergambit).

I'd recommend a fighting opening over a positional / theoretical one. That'll force your opponent to play precisely early on, something most players won't do. 
Here are my typical recommendations
- Slav
- Tarrasch 
- QGA 
- Benko (or Blumenfeld)
- English Defense
- Triangle Slav
- Possibly the Nimzo Indian combined with the Vienna, Blumenfeld, or Bogo

In general 1... Nf6 handles the junk better than 1... d5, but both are perfectly viable.

Those who play 1.d4 either go into a system opening, think London, Colle, Zukertort; or they want to play a mainline. So all you have to do is look at what you want to get out of an opening against the system players and then choose a good line against non system players. I tend to play the Dutch as it works well against system players and you get main line Dutch for non system players. But other things to consider are stonewall or semi-slav openings. Maybe play 1.d4 e6 and see what the other player does so you can avoid Staunton gambit, or go into a French if 2.e4.

triangle slav is one of the bests

Ok. Do u know the best ways to study these openings? Specific YouTubers are courses, etc?

*or

Oh I know of the videos. I just dont remember all the lines and variations. So 1.d4 isn't in my go to. 1.e4 is mine.

Bongcloud

megas is right, people usually dont play d4 unless they have a main line they want to play. I seriously recommend studying the Indian defenses, they are extremely helpful.

Books published within the last 5 years for heavily theoretical openings and 20 years for minor lines along with board and pieces on a tabletop. Not YouTube!

You should do the lessons on the openings you want to play.

Just...answer...1.d4...with...1.....d5!. If 2.c4 then just accept the QG and force white to prove your opening was a mistake. Raise the skinny fist! Release the squeeky voice of Krakken Rage! The power of dee five,once and forever,unstoppable!

Another way of doing the openings is to look through game database and make a selection of games from an opening. High elo and accuracy with different lines. Analyse why the moves work on both sides and then memorise the small selection as a guide so you know what you should be doing. One game at a time.

Leningrad is better than classical dutch Even according to the engine.

NO! Players should block anyone who wont play the QGA. It's an insult, a mockery to REAL chess to play those gobbbly wobbly whacko lines.

Stonewall is probably the best Dutch. If you start in a semi slav you transpose into it avoiding gambit lines like Staunton, Keres or Korchnoi, which 1.d4 f5. Only waiting line for Leningrad is the hypermodern opening 1.d4 g6 which leaves you open to h file attacks and set ups the KID faces. KID is probably better than Leningrad as well. I am also not sold on Leningrad being better in the judgement of the engine. Any time I went through it I found it prefered e6 over g6 when f5 had already been played. Main draw back of Stonewall is no chance for a queenside fianchetto; so minimal LSB activity until later on, or traded off. Classical Dutch can utilise ideas from Bogo Indian and Queens indian which still means it is flexable and not to be ruled out. If you know the whole scope of the Dutch you can play it against most things with no issue. Gambits are always the biggest problem, but transposition takes the sting out of them.

I strongly dislike the stonewall, mainly because its a half-win for the opponent from the first move. It's the same with that Maroczy defense where the queens come off in the opening,unless I'm playing a very low ranked player I feel vaguely insulted by those two openings.