For the "I" version, all three endings behave the same: chop off -ar, -er or -ir and add -o. For every other person, the verbs split into just two groups.
-ar verbs · -er / -ir verbs
Most Spanish verbs are -ar verbs, and that is the biggest group by far. In fact any new verb entering Spanish will be crowned an -ar verb.
-ar verbs have /a/ as their principal sound, the vowel that keeps popping up. Build the other people from it by adding to that a.
-o = I · -a = he/she/it/you (formal) · -an = they/you (plural) · -as = you (informal)
The accent stays on the penultimate syllable throughout. Adding n to the a gives they and also you plural, as in "you guys" or "you all".
No dura mucho · No exagera · No hablan con Pablo · Quiero hablar · Voy a hablar
Como also means how or like, by coincidence, as in ¿cómo estás? So como is both I eat and how.
Durar mucho · Dura mucho · Voy a hablar blends together when spoken quickly.
The small words te, me, lo, los, la, las come before the changed verb. A changed verb is one that no longer ends in r.
lo quiero (I want it)
When there is a "to" form in the sentence as well, you get a choice: attach it to the end of the "to" form, or put it before the changed verb. There is no difference in meaning at all.
But a changed verb standing on its own gives you no option: the little word must go before it.
Debo invitarlo / Lo debo invitar · Es importante hablarlo
For it's important to speak about it, you do not need a word for about. Just say to speak it and that is understood.
The teacher did not know the English word mastication. He found masticar first and met the English word later. The same happened with morder, to bite, and then mordent in a novel.
A word like eliminar is confusing taken all at once, because it has so many vowels. Taken syllable by syllable it is much more digestible.
Finding durar is a good example of the long route: to last gives you nothing, but "a period of time" gives you duration, then duración, then durar.