Он хорошенько подумал.

Here хорошенько is an adverb meaning something like properly, thoroughly, carefully, or for a good while.

So Он хорошенько подумал is not just He thought. It suggests He gave it some real thought or He thought it over well.

A useful point: хорошенько often adds a slightly conversational feeling, as if saying really or good and hard in English:

• хорошенько подумать = to think something over properly
• хорошенько выспаться = to get a really good sleep

This is a very common Russian aspect question.

• думал = imperfective
• подумал = perfective

In this sentence, подумал shows a completed act of thinking: he thought for a while and reached the end of that thinking episode.

Compare:

• Он думал. = He was thinking / He used to think / He thought
  This focuses on the process.
• Он подумал. = He thought for a bit / He gave it some thought
  This treats the action as a whole, as one completed event.

So Он хорошенько подумал means he spent some time thinking it over and that thinking is viewed as a complete action.

Подумал is:

• past tense
• masculine singular
• perfective
• from the verb подумать

Russian past tense agrees with gender and number:

• он подумал = he thought
• она подумала = she thought
• оно подумало = it thought
• они подумали = they thought

So the ending -л with no extra -а / -о / -и tells you it is masculine singular past.

Because Russian past tense is usually formed differently from English.

English often uses:

• did think
• has thought
• had thought

Russian normally just uses the past tense form of the verb:

• подумал

So Он подумал can cover meanings that English might express in different ways depending on context:

• He thought
• He gave it some thought
• He thought it over

Russian does not need an auxiliary verb like did or has in this sentence.

Russian often leaves out information that is understood from context.

So Он хорошенько подумал can stand on its own and mean:

• He thought it over carefully
• He gave it a lot of thought

If you want to say what he thought about, Russian can add it:

• Он хорошенько подумал об этом. = He thought carefully about it.
• Он хорошенько подумал над этим. = He thought this over carefully.

Without an object, the sentence still sounds natural if the topic is already known.

Yes, Russian word order is flexible.

The neutral order here is:

• Он хорошенько подумал.

This puts хорошенько naturally with the verb.

But other orders are possible, depending on emphasis:

• Хорошенько он подумал.
• Подумал он хорошенько.

These alternatives are more marked and may sound literary, contrastive, or context-dependent.

So for learners, the given order is the safest and most natural one.

Not exactly.

• хорошо = well
• хорошенько = really well / properly / thoroughly

In many contexts, хорошенько sounds more emphatic and often more conversational.

Compare:

• Он хорошо подумал. = He thought well or He thought carefully
• Он хорошенько подумал. = He really thought it through / He gave it proper thought

So хорошенько adds extra force.

The sentence is perfectly normal Russian, but хорошенько has a slightly colloquial or everyday flavor.

That does not mean it is slang. It just sounds less dry than some more neutral alternatives.

For example:

• Он тщательно обдумал это. = more formal/bookish: He considered it thoroughly
• Он хорошенько подумал. = more everyday: He gave it some real thought

So this sentence is natural in normal speech and informal writing.

The main stresses are:

• Он
• хорошЕнько
• подумАл

So roughly:

• on khara-SHEN'-ka padu-MAL

A more careful breakdown:

• хорошенько → stress on -ше-
• подумал → stress on the last syllable: -мал

If you want a natural rhythm, say:

• Он хорошЕнько подумАл.

Not always. In perfective form, подумать often means to think for a while, to give thought to something, or to think something over.

So in many contexts it is stronger than a simple dictionary gloss to think.

Examples:

• Я подумаю. = I’ll think about it.
• Он немного подумал. = He thought for a bit.
• Он хорошенько подумал. = He thought it over carefully.

So here the idea is not just that thoughts passed through his mind, but that he spent time considering something.