This doesn’t pass the smell test. There’s COUNTLESS grifters that will sell you some “natural” way to “cure” whatever ailments you might have. ADHD is medically recognized and most certainly not treated with vitamin B because there’s no literature to back that up as an effective strategy.
If there was double-blind peer-reviewed studies that suggested vitamin B deficiency had any reasonable correlation with ADHD we would already be treating it with supplements that way.
Can I ask where you got this information?
A licensed doctor/psychiatrist is the only one that can actually diagnose you. There’s many differential diagnoses for something like ADHD. My advice is to talk to a doctor and they can give you an official assessment and your options.