Ground :
3.3V :
5V :
This is strange
Try to do this in the setup before
analogReference(AR_INTERNAL)
I will try, i never (or almost) did schematics before, as i said earlier i don't know the specifics of the IR transmitters so i don't know how to do a drawing of it, but here it is the system i was trying to use to read the modulated signal :
When i was trying the TSOP32238 i did something simple like this
How have you now determined thta is is modulated?
I didn't you are right, but when i asked the people who where in the party of those who did this remotes and the receiver (as they are old the ones that did them are probably not with us anymore) they talked about modulated signal, so i just trusted blindly.
Ground :
3.3v :
I didn't do the 5v since the 3.3v was already at 5v and i was caution to the damage it would have caused in the arduino.
That could mean anything. Just turning light on an off is considered modulation.
If it is actually a 38kHz modulated carrier, you photodiode circuit won't work.
If it was an modulated signal at 38kHz i guess the TSOP32238 would be able to identify the signal.
And my photodiode isn't working anyway, i can't put it to work.
I wouldn't bet on that.
So did you try receiving one LED by one?
Not necessarily depends on the modulation sequence.
Without a scope you are just floundering in the dark
I tried but i couldn't hide one of the LEDs, it received always the same signal, idk if it was because i was doing it poorly or not.
What scopes would you recommend?
I would like to buy but the money doesn't come from me it comes from the company, i can't ask them to but something really expensive, plus there isn't everything sold here, it must be something that is sold in portugal nerby where i'am at, or else it would take too long to arrive and i would lost weeks for nothing in my internship.
If you have any scope recommendations please let me know.
The 4 photodiodes should give you a big hint that you are not dealing with a plain old TV remote.
Shouldn't be complicated... 
By the way, why is your arduino ADC reading GND as 300?
It is normally reading at ~128 but i added this line code on my setup :
analogReference(AR_INTERNAL)
And it went to ~300
I don't know your board, but shouldn't it read 0 in any case?
I have no idea what is available locally to you.
This is the main place where i buy all my stuff : https://mauser.pt/
The site is in portuguese but if you search for the components reference you will find them.
Company paid scope is great option, but pick one of those 30-60kHz learner receivers as well (TSMP98000).
As i told you that TSMP isn't sold in my region neither the other one you suggested, unfortunally, is there any other equivelent ??