The Portuguese words you already know

Portuguese and English share their Latin layer rather than having borrowed from one another. English acquired it through Norman French and through scholarly Latin; Portuguese inherited it directly as a descendant of spoken Latin. Both ended up with the same abstract vocabulary from the same source.

The -ção ending looks unfamiliar and is completely regular: it is the same Latin -tionem that produced English -tion and Spanish -ción. Once you read the tilde as a nasal rather than as an obstacle, the whole family becomes transparent.

Portuguese is also the closest major language to Spanish, so anyone who has studied Spanish arrives with a second layer of recognition on top of the English one.

Written recognition runs well ahead of listening. European Portuguese in particular reduces unstressed vowels heavily, so a word that is obvious on the page can vanish in speech - more so than in Spanish or Italian.

Brazilian and European Portuguese differ in spelling for some words and in vocabulary for others. The lists here follow Wiktionary, which covers both, so an entry may occasionally be the variant you are not learning.

The false friends overlap with the Spanish ones but are not identical, and a few of the divergences catch out precisely the people who already speak Spanish.

Learn -ção first and read it aloud a few times until the nasal stops being strange. It is the highest-yield single rule in the pair.

Add -idade and -oso, and you have most abstract nouns and a large share of adjectives.

If you already speak Spanish, work through the false friends rather than the cognates. The shared vocabulary will take care of itself; the divergences are where the errors live.