I can't decide the perfect method for you; I'm stating I personally wouldn't recommend OD as a method for you. But you can do whatever you want ofc
Why exactly do they fail then?
Is it cause they were found or their body was too strong or something else?
Long story short: Drugs & combinations of drugs work differently for everyone, and it is difficult to gauge. Lots of different factors and reasons. Perhaps you could use the search button, see if other users have shared their experiences (I'm not too sure, I haven't looked it up myself - I'm answering based on personal experiences and observations from people around me)
How are they more likely to die if they don't even plan to suicide?
Some people use hard drugs recreationally, sometimes excessively, some are addicts. They use drugs for fun and to get high or for escapism
Not everyone who has died from overdosing has intended to suicide. Lots of people die due to accidents.
Tolerance to drugs builds up, and can change/fluctuate depending on someone's use of drugs and sometimes they miscalculate it.
Sometimes the drugs they bought off the streets/black market has been laced with something else, or they got sold something else etc.
Many people say that the questions I ask are stupid, I think this is cause I have no abilities at all in real life, the only things I can do are online, I have no irl skills that is why basic things are hard for me I think.
I didn't say the questions that you asked are stupid, but they are really basic things.
People might be able to answer technical questions about a specific method once you have done enough research (
look up at what others have posted, read the megathreads and resources thread etc.) based on your current circumstances,
but it would be quite difficult for people to answer random questions about your living situations etc. or how to figure out how to do a basic chore in a house they don't live in, in a suicide section; and
OD-ing - in general, not just for you - is something that is quite unreliable as a method, it rarely succeed. On the flip side, incidents do happen.
Hope that answers your questions.