How did ancient desert people survive their long journeys through a desert?

I love the idea of ancient people traveling through sandy deserts, its very dreamy and interesting. But I have alot of questions about it I cant find anything about.

1) How long would a desert journey take. Ive heard weeks, months, years even. How large can deserts be ? I mean like real soft sand wavy deserts.
2) How did they they get food/water. A person can go 3 days without water, and 30 without food right. In a desert Id imagine thatd be less. I assume they would bring alot of supplies with em, on the camels. But water, for months doesnt it drie up a certain point, did they puth it in vases..... How did they do that exactly.
3) Didnt they need to feed the camels too, I read that a camel can go without water a week, and without food for months. Thats handy but you still need to feed them alot of water if youre gone for months then right ?

How did caravans take all those supplies with em ? I would imagine you would need like a giant sand sled thats too heavy to even pull. Can someone shed some light on this.

You dont need to answer everything, if you just know something thats enough.

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