Which sect of Buddhism has the true teachings of Buddha?

Many people (myself included in the past) are today unfortunately confusing real Buddhism with a sect that split off of it called Mahayana. Buddha taught how to achieve enlightenment in this lifetime. In fact, a number of his students became enlightened instantaneously upon hearing his teachings (even just one sentence: things happen due to conditions, or, in the seen there's only the seen. in the heard, only the heard. no you in any of that, as per the Bahiya sutta.) 

Mahayana Buddhism teaches that we should put OFF enlightenment so that we can remain here for countless lifetimes to help others. This is actually not exactly against what Buddha taught, but he referred to people who thought this way as people who were foolish and wanted to suffer, even tho he respected them and was himself one of those people (called Bodhisattvas), unknowingly, in his past lives, which is how he became a Buddha, which is not just an enlightened being, but a world-teacher (turner of the wheel of dhamma, as they say). 

The Mahayana sutras are "fake" because they say "Buddha said this" but in fact he never did say that--this is what meditators apparently saw him say in their visions or something like that. Some Mahayana monks actually converted to Theravada after they found out the sutras were fake. 

I've experienced (actually not me, but reality itself without me) Nibbana, which is totally infinitely perfect, disjoint, witnessless reality, every flowing process knowing itself, on various occasions, so I'm not just some believer or theorist or something like that. What Buddha taught is very simple, very scientific, and it works.

Even more troublesome tho, than the Mahayana bodhisattva emphasis, is the very frequent tendency in many Mahayana sutras to teach the OPPOSITE of Buddha's teaching of no-self or anatta. They actually teach there is a True Self and a One Universal Mind (in fact these are just stages of insight before no self), in the sutras which talk about the Tathagathagarba, which originated with Buddha's teaching that there is a "luminous mind" which is defiled only by environmental influxes. Yes, there indeed is such a thing, and I've experienced that. But, as Ajahn Mun supposedly taught Mae Chee Kaew, but failed to teach Ajahn Maha Bua, that is only a pothole on the road, not some indestructible essential perfection. Ajahn Mun himself seems to have been confused about this at one point as well, tho the timing of his realizations is unclear.

A good book to read is "What the Buddha Taught" by Walpola Rahula. That really sums everything up pretty clearly, but if you want a book geared more towards how to meditate, I suggest "Mindfulness, bliss, and beyond" by Venerable Ajahn Brahm.

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There's also a more subtle and maybe respectful explanation of this topic from a Theravadan monk here.