Thánh rất tốt.

Vietnamese often uses adjectives directly as the predicate, so you do not need a separate word for is here.

So the pattern is:

• subject + adjective
• subject + rất + adjective

That is why Thánh rất tốt naturally means Thánh is very good.

Vietnamese usually does not use là before an adjective. Là is mainly used when the predicate is a noun, for example:

• Thánh là bác sĩ. = Thánh is a doctor.

Rất means very.

In Vietnamese, rất normally goes before the adjective it modifies:

• rất tốt = very good

So the order is different from English only in the sense that Vietnamese keeps the intensifier directly before the adjective.

A useful comparison:

• rất tốt = very good
• tốt lắm = also very good, but lắm goes after the adjective

Both are natural, but the word position is different.

Normally, no.

With an adjective predicate, standard Vietnamese does not use là. The natural sentence is:

• Thánh rất tốt.

A good rule is:

• subject + adjective → Thánh tốt
• subject + rất + adjective → Thánh rất tốt
• subject + là + noun → Thánh là bạn tôi

So là fits with nouns, not usually with adjectives like tốt.

The capital letter by itself does not prove it is a name, because Vietnamese capitalizes the first word of a sentence anyway.

So at the start of a sentence, Thánh could be:

• the common noun thánh
• or a personal name / nickname in some contexts

You have to rely on the meaning or context already given to you. Grammatically, the sentence structure works the same either way.

Vietnamese does not use articles the same way English does. Often, context is enough.

So Vietnamese may simply say:

• thánh

without adding a separate word for a or the.

If you want to be more specific, Vietnamese can add other words, for example:

• một vị thánh = a saint
• vị thánh đó = that / the saint

If Thánh is a person’s name, then articles would not be used anyway.

A few helpful points:

• All three words have the sắc tone, which is a rising tone.
• Thánh: roughly tahnh, with -nh similar to the ny sound in canyon
• rất: a short syllable with a clipped final -t
• tốt: roughly toht, also with a clipped final -t

One more note about rất:

• in northern Vietnamese, r often sounds somewhat like English z
• in southern Vietnamese, it is often closer to English r

So the full sentence has three rising-tone syllables in a row, which can take practice.

No. Tốt is very common, but English uses good in many different ways, and Vietnamese often uses different words depending on the meaning.

For example:

• tốt = good, kind, of good quality
• giỏi = good at something, skilled
• hay = good / interesting / enjoyable for songs, films, books
• ngoan = good in the sense of well-behaved

So tốt is correct in many cases, but it is not the universal translation for every use of good in English.

To make it negative, put không before the adjective:

• Thánh không tốt. = Thánh is not good.

To ask a yes/no question, a very common pattern is có ... không:

• Thánh có tốt không? = Is Thánh good?

In everyday speech, people also often say:

• Thánh tốt không?

Both are natural, and the second one is shorter and more conversational.