Мне нравится, что авокадо подходит и для салата, и для быстрого завтрака.

Because нравиться works differently from English to like.

Russian structures it as something pleases someone:

• Мне нравится авокадо = Avocado is pleasing to me = I like avocado
• Мне нравится, что... = I like that...

So:

• мне = to me
• нравится = is pleasing / is liked

By contrast, я нравлюсь means I am pleasing / someone likes me.

With нравиться, the person who experiences the liking goes in the dative.

So:

• мне = to me
• тебе = to you
• ему / ей = to him / her

This is one of the most important patterns to remember with нравиться:

• Мне нравится книга.
• Ей нравится кофе.
• Нам нравится, что...

Because here what is being liked is the whole clause:

что авокадо подходит и для салата, и для быстрого завтрака

That entire idea is treated as a single thing, so Russian uses singular нравится.

Compare:

• Мне нравится авокадо. — singular
• Мне нравятся авокадо и манго. — plural things
• Мне нравится, что авокадо подходит... — one whole fact/idea

Here что means that and introduces a subordinate clause.

So the structure is:

• Мне нравится, что... = I like that...

It connects the main statement with the specific fact that follows:

• Мне нравится = I like it
• что авокадо подходит... = that avocado works/is suitable...

In Russian, subordinate clauses are normally separated by a comma.

So in:

Мне нравится, что авокадо подходит...

the comma marks the beginning of the clause introduced by что.

This is much more regular in Russian than in English. Even where English might sometimes omit punctuation, Russian usually keeps the comma.

Here подходит means something like:

• is suitable
• works well
• is good
• is appropriate

So авокадо подходит для салата means avocado is suitable for salad or works well in salad.

Be careful: подходить can also mean to approach / come up to, but that is a different meaning. Here it is clearly the to suit / to be suitable meaning.

The preposition для takes the genitive case.

So:

• салат → для салата
• быстрый завтрак → для быстрого завтрака

That is why both nouns change after для.

This structure means for in the sense of for the purpose of / suitable for.

Because adjectives must agree with the noun they describe in case, number, and gender.

Here:

• dictionary form: быстрый завтрак = a quick breakfast
• after для: для быстрого завтрака

Both the adjective and noun go into the genitive singular:

• быстрый → быстрого
• завтрак → завтрака

This is a very common correlative pattern meaning both ... and ....

So:

и для салата, и для быстрого завтрака

means:

• for salad and for a quick breakfast
• more literally: both for salad and for a quick breakfast

Repeating и gives a balanced, slightly emphatic structure.

Compare:

• для салата и для завтрака — also possible
• и для салата, и для завтрака — both for salad and for breakfast

Авокадо is usually treated as an indeclinable noun in Russian, so its form often stays the same in different cases.

In this sentence it is the subject of подходит, so nominative is expected anyway, but even in many other contexts the form remains авокадо.

It is also normally treated as neuter singular:

• спелое авокадо
• вкусное авокадо
• авокадо подходит

Usually not in the same meaning.

• подходит для = is suitable for / is good for use as
• подходит к = goes with / matches / suits alongside

So:

• авокадо подходит для салата = avocado is suitable for making/using in salad
• авокадо подходит к салату would sound more like avocado goes well with a salad, which is a different idea

In this sentence, для is the natural choice because avocado is being described as something that works well as part of those meals.

Not completely. Russian word order is flexible, but this version is natural and neutral:

Мне нравится, что авокадо подходит и для салата, и для быстрого завтрака.

The end of the sentence highlights the two uses of avocado. You could move things around for emphasis, but the given order sounds smooth and standard.

For example, a speaker might say:

• Мне нравится, что и для салата, и для быстрого завтрака подходит авокадо.

This is grammatical, but it sounds more marked and puts stronger focus on the two purposes.

Yes. Завтрак usually means breakfast, and depending on context it can refer to:

• the meal/time of day
• the food eaten for breakfast

In this sentence для быстрого завтрака is understood as for a quick breakfast in a practical sense: avocado works well as breakfast food or as part of a quick breakfast.

Yes, it is natural and idiomatic.

It sounds like something a native speaker could easily say when talking about food preferences or why they like avocado. The structure is especially natural because Russian often uses:

• Мне нравится, что...
• подходит для...
• и ..., и ...

So the sentence is a good example of everyday, useful Russian.