I heard halloween is a druid celebration.
Kinda, kinda not. Samhain was and is a traditional Gaelic festival, and its origins in pre-Roman Celtic culture is attested through a few inscriptions and writings. But the druids weren't necessarily synonymous with the public religion of the ancient Celts, so I would be hesitant with using "druid" or "Druidic" to describe everything ancient and Celtic. There's still a great deal we don't know about how the Celts practised their religion, and what role the priestly caste had in their daily religious lives.
In any case, we don't know much of what Samhain was supposed to have meant to the ancient Celts, what it signified, and what its celebration consisted of. By the time we have verifiable written descriptions of what the Irish did on Samhain, they had been Christianized. So it's not really easy to tell what parts are All Saint's Day and what parts are Samhain.
Halloween is deeper than a christian "angle". Halloween was sacred to the Druids because their sun-god receded to the underworld on October 31st.
In addition to the stuff I mentioned above, I'll also point out that Samhain wasn't a solar festival. In fact, the Celts don't really seem to have significant solar festivals. Their liturgical calendar, if the ones found could be described as such in the first place, as framed around lunar cycles and agricultural seasons.
Further, the "dying and rising god" thing isn't as widespread as that. It's an idea extrapolated by James Frazer out of a few selected myths. But most of those myths pertain to the Mediterranean and Near Eastern cultures and their environment. Europe north of the Alps has a very different climate, and the Celts wouldn't have necessarily shared in the same mythological patterns as the Romans and Greeks. This assumes that the Frazerian myth really can be extrapolated, and wasn't him constructing evidence to fit his theory on how religions evolved in ancient societies.