I saw this word in the grammar guide and was quite confused because it seemed counter intuitive to how I thought about the prefix 'mal'.
So the word is 'ne-mal-hav-ebl-a' which is quite a lot.
'havebla' would mean haveable. And so in my mind since 'mal' denotes the opposite, 'malhavebla' would be 'unhaveable' but that doesn't seem to be the case. Apparently it's 'dispensable' and so 'nemalhavebla' is 'indispensable'. But then what is 'unhaveable' in esperanto?
Is this just counter intuitive for me or is this one case of 'you just have to learn it'? Are there more of those weird ones?

I´m new so to Esperanto, so I might not be getting this right.

First, the word for ´unhaveable´ would be ´nehavebla.´ Literally ´not having possible.´

Second, I think what is going on with ´nemalhavebla´ is that the ´ne-´ is modifying the ´-mal-´ so that it comes out literally as something like ´not unhaving possible´ or indispensable.

Something you can't do without.