Questa ciliegia è molto dolce.

Because ciliegia is a feminine singular noun, and the demonstrative questo (this) has to agree with it.

The forms are:

• questo = masculine singular
• questa = feminine singular
• questi = masculine plural
• queste = feminine plural

So:

• questa ciliegia = this cherry
• questo libro = this book

In Italian, nouns have grammatical gender, and ciliegia is feminine. One clue is that many nouns ending in -a are feminine, though this is not a perfect rule.

You can usually see the gender through the words around the noun:

• questa ciliegia
• una ciliegia
• la ciliegia

All of those show that ciliegia is feminine.

Because questa already works as a demonstrative determiner, like this in English.

In English, you say:

• this cherry

not:

• the this cherry

Italian works the same way here:

• questa ciliegia

not standard Italian:

• la questa ciliegia

So the article is not needed.

The accent is important because è means is, while e without an accent means and.

So:

• è = is
• e = and

This is a very common spelling point in Italian.

Here molto is an adverb meaning very, so it does not change for gender or number.

It modifies the adjective dolce:

• molto dolce = very sweet

Compare that with molto used as an adjective meaning much/many, where it does change:

• molta acqua = a lot of water
• molti libri = many books

But in è molto dolce, it stays molto because it means very.

Because some Italian adjectives have the same singular form for both masculine and feminine. Dolce is one of them.

So you get:

• un frutto dolce = a sweet fruit
• una ciliegia dolce = a sweet cherry

In the plural, it changes to:

• dolci

So:

• ciliegie dolci = sweet cherries

This is the most normal word order:

• subject + verb + adverb + adjective

So:

• Questa ciliegia = subject
• è = verb
• molto dolce = description

Italian can sometimes change word order for emphasis, but this version is the standard, neutral one.

Yes, if the context is clear.

Italian often leaves out things that are obvious from the situation. If you are holding the cherry or have just been talking about it, È molto dolce can be perfectly natural.

But if you want to clearly identify this cherry, then Questa ciliegia è molto dolce is better.

It is pronounced roughly like chee-LYE-jah in English approximation, though the real Italian sound is more precise.

A few useful points:

• ci before i/e sounds like ch in church
• gli in ciliegia is part of the spelling, but here the word is pronounced approximately ci-lie-gia
• the stress falls on lie

A common approximate pronunciation is:

• chee-LYE-jah

The plural is ciliegie.

So:

• questa ciliegia = this cherry
• queste ciliegie = these cherries

Notice:

• feminine singular: questa
• feminine plural: queste
• singular adjective: dolce
• plural adjective: dolci

So the full plural version would be:

• Queste ciliegie sono molto dolci.

Yes. Dolcissima means very sweet or extremely sweet and uses the Italian superlative ending -issimo/-issima.

So both are correct, but they feel slightly different:

• molto dolce = very sweet
• dolcissima = extremely / really sweet

Because ciliegia is feminine singular, the form is dolcissima.

It normally refers to one specific cherry, because of questa (this).

So it means you are pointing out or identifying a particular cherry.

If you wanted to talk about cherries in general, you would use a different structure, for example:

• Le ciliegie sono molto dolci. = Cherries are very sweet.

So questa makes it specific, not general.