What this suffix does
The suffix -al takes a noun and creates an adjective meaning "related to", "characteristic of" or "belonging to". From "nation" you get "national"; from "music" you get "musical"; from "origin" you get "original".
It is one of the most frequent suffixes in academic, scientific and professional vocabulary. When you see a long adjective ending in -al, strip it off and look for the noun inside.
The easiest suffix for Spanish speakers: -al = -al
This suffix has the most direct cognates of any in English. In the vast majority of cases, the English -al word is identical or near-identical to the Spanish one:
national = nacional
musical = musical
original = original
natural = natural
normal = normal
Pronunciation differs (English -al is unstressed), but the words are practically the same. If Spanish uses a -al adjective, the English version exists and is spelled almost identically.
-al can also function as a noun
Some -al words work as both adjectives and nouns:
an animal, a proposal, a signal, a trial, a journal.
Context tells you which function the word is serving. The form is exactly the same.