O índice está claro, mas o ícone do documento continua estranho.

Yes. In this sentence, índice, ícone, and documento are all masculine singular nouns, so they take o.

A useful thing to remember is that noun gender in Portuguese is not always obvious from the ending:

• o índice = masculine
• o ícone = masculine
• o documento = masculine

So you should learn each noun together with its article: o índice, not just índice.

Portuguese often uses estar for a current state, condition, or appearance.

So:

• está claro = it is clear right now / it appears clear
• é claro = it is clear in a more general, permanent, or obvious sense

In this sentence, o índice está claro suggests that the index is currently clear or easy to understand, rather than expressing a timeless fact.

Here, claro means clear, easy to understand, or visually easy to read.

Portuguese claro can have several related meanings depending on context, including:

• clear
• light in colour
• obvious

In o índice está claro, it most naturally means that the index is clear in presentation or understandable.

Mas means but.

It connects two contrasting ideas:

• O índice está claro = the index is clear
• o ícone do documento continua estranho = but the document icon still looks strange

So mas works just like English but.

Because de + o contracts to do in Portuguese.

This is one of the most common contractions:

• de + o = do
• de + a = da
• de + os = dos
• de + as = das

So:

• o ícone do documento = the icon of the document / the document icon

You normally must make this contraction in standard Portuguese.

Portuguese usually does not stack nouns the way English does.

English often uses noun + noun combinations:

• document icon
• computer screen
• file name

Portuguese normally expresses that relationship with de:

• ícone do documento
• ecrã do computador
• nome do ficheiro

So o ícone do documento is the natural Portuguese structure.

Continua estranho means continues to be strange or still looks strange.

The verb continuar already carries the idea of something remaining the same, so Portuguese often does not need a separate word for still.

• continua estranho = it remains strange / it is still strange

If you wanted, Portuguese could also use ainda in some contexts, but here it is not necessary because continua already gives that sense.

Because the subject is already stated: o ícone do documento.

Portuguese does not need a separate dummy subject like English it when the real subject is present.

Structure here is:

• O índice = subject
• está claro = verb + adjective
• mas
• o ícone do documento = subject
• continua estranho = verb + adjective

So Portuguese simply says the noun phrase directly, without adding an extra pronoun.

Because they agree with the nouns they describe.

In Portuguese, adjectives usually match the gender and number of the noun:

• o índice → claro
• o ícone → estranho

If the noun were feminine, the adjective would often change:

• a ideia está clara
• a imagem continua estranha

This agreement is a very important part of Portuguese grammar.

Continua is the 3rd person singular present of continuar.

That means it matches a singular subject such as:

• o ícone continua
• o documento continua
• ele continua

In this sentence, the subject is o ícone do documento, which is singular, so continua is the correct form.

The accent marks help show pronunciation and, in some cases, distinguish words.

• índice: the stress falls on the first syllable
• ícone: the stress falls on the first syllable
• está: the accent marks the stressed final syllable

In está, the accent also helps distinguish it from esta, which is a different word.

Accent marks are very important in Portuguese because they often tell you where the stress goes.

Yes, it is natural and grammatical.

A European Portuguese speaker would understand it as a normal contrast between two interface elements or parts of a document:

• one thing is clear
• the other still seems odd

If you are thinking in a digital or software context, the wording is perfectly plausible. The only thing that may vary slightly is vocabulary preference in different settings, but the sentence itself is fully natural.

In European Portuguese, several unstressed vowels are reduced, so it may sound more compressed than a learner expects.

Very roughly:

• O índice está claro
• mas o ícone do documento continua estranho

A few useful pronunciation notes:

• o often sounds closer to u when unstressed
• de / do can sound quite reduced
• unstressed vowels in words like documento and continua are often weakened
• estranho has the nh sound, like Spanish ñ or the ny in canyon

So the sentence may sound faster and less fully pronounced than its spelling suggests.