Va li này nặng.

Because Vietnamese often does not use a separate verb like to be before adjectives.

So:

• Va li này nặng = This suitcase is heavy
• literally, it looks more like suitcase this heavy

In Vietnamese, adjectives such as nặng can directly describe the subject without needing is.

No. That would not be the normal way to say it.

Là is usually used to connect one noun to another noun, as in:

• Anh ấy là bác sĩ = He is a doctor

But with adjectives, Vietnamese normally does not use là:

• Va li này nặng = This suitcase is heavy
• Cô ấy đẹp = She is beautiful
• Trời lạnh = The weather is cold

So here, là should be left out.

Because Vietnamese demonstratives usually come after the noun.

So:

• va li này = this suitcase
• người này = this person
• nhà này = this house

This is a very common difference from English, where this comes before the noun.

Here, này means this.

It points to something near the speaker, or something the speaker is referring to directly. In contrast:

• này = this
• đó = that
• kia = that over there / that one farther away

So va li này is the normal way to say this suitcase.

Yes, very often.

Vietnamese adjectives usually come after the noun they describe:

• va li nặng = heavy suitcase
• nhà lớn = big house
• xe mới = new car

In Va li này nặng, nặng comes after va li này because it is the description of the suitcase.

Yes, absolutely.

Cái is a classifier commonly used for many objects. So both of these are possible:

• Va li này nặng
• Cái va li này nặng

Adding cái can make the noun phrase feel a little fuller or more explicit. In everyday Vietnamese, classifiers are often used, but they can also be omitted in some contexts.

Both spellings exist.

• vali is very common in modern Vietnamese
• va li is also seen and understood

They mean the same thing: suitcase.

So the sentence could also be written as:

• Vali này nặng.

A rough guide is something like nahng, but with an important tone.

A few pronunciation points:

• ă is a short vowel
• ng sounds like the end of English song
• the dot below the vowel marks the nặng tone, which is low and heavy, often with a cut-off or glottalized feeling

So nặng is not just the sounds n + ang. The tone is an important part of the word.

Not in the same way as in English.

Vietnamese does not use articles exactly like a/an/the. Instead, meaning comes from context and from words like này.

So:

• va li can mean a suitcase or the suitcase, depending on context
• va li này clearly means this suitcase

That is why the sentence can be short and still sound complete.

No. Vietnamese nouns usually do not change form for singular or plural.

So va li stays va li. If you want to make plurality clear, Vietnamese usually adds another word, such as:

• những va li này = these suitcases
• các va li này = these suitcases

In your sentence, va li này is understood as singular because of này and the context.