do que or que = than
e.g.
O tempo de hoje está mais frio (do) que o de ontem. Weather today is colder than weather yesterday.
The superlative
Use definite article in front of superlative:
Hoje é o dia mais frio do ano. Today is the coldest this year.
Some
exceptions:
bom - melhor good - better mau - pior bad - worse grande - maior big - bigger pequeno - menor small - smaller
Absolutive superlative
Absolutive superlative can be formed two ways:
analytical (muito before the adjective)
synthetical (-íssimo added to the adjective)
analytical (superlativo absoluto analítico)
Formed by adding adverb before the adjective (usually muito, but other adverbs are used also).
muito caro
NOTICE: This form is used used usually in colloquial speech.
synthetical (superlativo absoluto sintético)
Absolutive superlative is made with íssimo-ending:
caro, muito caro, caríssimo
expensive, very expensive, extremely expensive
NOTICE: The ending of the adjective may change as -íssimo ending is added to it. For example calmo >> calmíssimo, feliz >> felicíssimo.
Irregular absolutive
superlatives:
fácil - facílimo the easiest difícil - dificílimo the hardest mau - péssimo the worst bom - ótimo the best
From:https://www.dbfei.com/Article/putaoyayu/201311/8414.html