Saber is to know. The British slang he's got savvy comes from Latin, and it is the same root: "he's got saber", he's got savvy.
Saber is spelled with a b while English says savvy with a /v/, so you can see the v and b connection crossing between the two languages. It is a b here, so give it a b sound.
Quiero saber · No quiero saber · Quiere saber · No quiere saber
Change the -o to an -e and I want becomes he wants, she wants, or formal you want.
¿Por qué no quiere saber? · Quiero saber por qué no quiere saber
Sí is yes, and the same word is also if.
Quiero saber si quiere saber · Quiero saber si quiere invitarme
English has explanation, but Spanish does not follow it. It is explicación, not "explanación", so the verb is explicar.
explicación → explicar (to explain)
English carries the same c root, though: we say explain but then inexplicable, which in Spanish is inexplicable.
Spanish also lets you say I want to explain you something directly, where English more commonly puts it as "I want to explain something to you".
Pero quiero explicar · Pero quiero explicarte algo
The /j/ becoming /kh/ rule applies to justificación.
No quiero imaginarlo · No intento justificarme · Quiero iniciarlo ahora · ¿Por qué no quiere informarme?
Long sentences look overwhelming and unsayable. Divide them up and they are simple. Put 100% of your mental energy on the piece in front of you, say it, then let it go and look at the next piece. Once you have said a block you do not need to hold on to it.
quiero saber · por qué · no quiere · venir a la casa · a visitarme
Quiero saber por qué no quiere venir a la casa a visitarme.
Note the a before visitarme: even with a la casa sitting in between, you are still connecting to the feeling of venir, a verb of movement.
When you understand a Spanish sentence, saying it back in whatever English feels comfortable to you is exactly right. Why doesn't he want to let me know? is as good as why doesn't he want to inform me?