Маленький мальчик потерял мяч, но потом нашёл его под скамейкой.

Yes. Маленький мальчик is the subject of the sentence: the little boy.

Both words are in the nominative singular masculine form because they describe who did the action.

• маленький = little, small
• мальчик = boy

The adjective маленький agrees with мальчик in:

• gender: masculine
• number: singular
• case: nominative

So Russian uses matching endings to show that маленький describes мальчик.

Потерять is the infinitive: to lose.

In the sentence, we need a finite verb meaning lost, so Russian uses the past tense form:

• потерять = to lose
• потерял = lost

The ending -л is typical of past tense, and the form потерял is masculine singular, because the subject is мальчик, a masculine singular noun.

Compare:

• мальчик потерял = the boy lost
• девочка потеряла = the girl lost
• дети потеряли = the children lost

It actually is in the expected case already: accusative.

The verb потерять takes a direct object, so мяч is the thing being lost. For many masculine inanimate nouns, the accusative singular looks exactly the same as the nominative singular.

So:

• nominative: мяч = ball
• accusative: мяч = ball

Because мяч is masculine and inanimate, there is no visible change here.

Но потом means but then / but later / but afterwards.

• но = but
• потом = then, afterwards, later

Together they show contrast plus sequence:

• first: he lost the ball
• then: later, he found it

You could think of it as:

• но adds the contrast
• потом adds the time progression

So the sentence does not just mean two facts; it tells a little story.

The correct pronunciation is нашёл, with ё.

• найти = to find
• нашёл = found

In many Russian texts, especially informal ones, ё is often written as е, so you may see нашел. But it is still pronounced нашёл.

For learners, it is helpful to remember that:

• ё tells you where the stress goes
• it also affects pronunciation

So in careful learning materials, нашёл is the best spelling to notice.

Because the sentence needs him/it, not he.

Here его refers back to мяч and means it.

• он = he / it, as a subject
• его = him / it, as an object

In this sentence, the boy found the ball, so the ball is the object of нашёл. That is why Russian uses его.

You can think of it like this:

• Он нашёл мяч. = He found the ball.
• Он нашёл его. = He found it.

Even though мяч is inanimate in English, Russian still uses the grammatical gender system, and мяч is masculine, so the pronoun is его.

Because the preposition под often requires the instrumental case when it means under in the sense of location.

So:

• скамейка = bench
• под скамейкой = under the bench

The noun changes to instrumental singular:

• nominative: скамейка
• instrumental: скамейкой

This is a very common pattern:

• под столом = under the table
• под машиной = under the car
• под скамейкой = under the bench

So the ending -ой shows the instrumental case here.

No. Под can take different cases depending on meaning.

Most commonly:

• под + instrumental = location, under
• под + accusative = motion toward a position under something

In this sentence, the ball is already located there when it is found:

• под скамейкой = under the bench

But if there were movement to that position, you could get accusative:

• положить мяч под скамейку = to put the ball under the bench

So case helps show the difference between:

• where something is
• where something goes

Because both actions were done by the same subject: маленький мальчик.

The subject is:

• singular
• masculine

So both past tense verbs match that subject:

• потерял = lost
• нашёл = found

In Russian past tense, verbs agree with the subject in gender and number.

Compare:

• мальчик потерял, нашёл = boy, masculine singular
• девочка потеряла, нашла = girl, feminine singular
• дети потеряли, нашли = plural

Yes. Both are perfective past tense forms.

• потерять = to lose, perfective
• найти = to find, perfective

Perfective verbs present actions as completed events. That fits this sentence well:

• he lost the ball
• then he found it

The sentence tells us about two finished actions in sequence.

This matters because Russian often uses aspect to show whether an action is:

• completed / whole → perfective
• ongoing / repeated / process → imperfective

Here, the point is the completed result of each action, not the process.

Yes, Russian word order is fairly flexible.

The given sentence is natural and neutral:

Маленький мальчик потерял мяч, но потом нашёл его под скамейкой.

It starts with the subject, then the verb, then the object, which is easy and common.

But Russian could rearrange parts for emphasis, for example:

• Маленький мальчик потерял мяч, но потом под скамейкой нашёл его.
• Мяч маленький мальчик потерял, но потом нашёл его под скамейкой.

These alternatives may sound more marked or emphasize different information. For a learner, the original version is the most straightforward and natural.

In some contexts, Russian can omit an object if it is obvious, but here его is very natural and helps make the sentence clear.

• нашёл его под скамейкой = found it under the bench

Without его, the sentence is still understandable in the right context, but it may sound less complete on its own. Since this is a standalone sentence, keeping его is the normal choice.

So:

• with его = clearer, standard
• without его = possible in context, but less explicit

It most naturally describes where the ball was found: under the bench.

So the meaning is:

• the boy found it
• and it was under the bench

Grammatically, под скамейкой attaches to the action нашёл, but semantically it tells you the location of the object he found.

In ordinary understanding, this means:

• the ball was under the bench
• not necessarily that the boy was under the bench