La commode est lourde, alors je ne la déplace jamais seul.

Lourd(e) has to agree in gender and number with the noun it describes.

• La commode is feminine singular (because commode is a feminine noun).
• So the adjective must also be feminine singular: lourde (with -e).

If the noun were masculine, e.g. le canapé, you’d say:

• Le canapé est lourd.

In this sentence, alors means “so / therefore” and introduces a consequence:

• La commode est lourde, alors je ne la déplace jamais seul.
  → The chest of drawers is heavy, so I never move it by myself.

Alors and donc often overlap:

• alors is a bit more conversational and can also mean “then”, “in that case”.
• donc can sound a bit more logical or structured, like “therefore”, “so”.

You could also say:

• La commode est lourde, donc je ne la déplace jamais seul.

Both are correct; in everyday speech alors is extremely common.

La is a direct object pronoun meaning “it / her”.

• It replaces a feminine singular noun: here, la commode.

• Instead of repeating la commode, French uses a pronoun:

  • Je ne déplace jamais la commode. → full noun
  • Je ne la déplace jamais. → pronoun replacing la commode

Word order: in a simple tense, object pronouns go before the verb:
je la déplace, je ne la déplace pas, etc.

Jamais is one of the words that can replace pas in negation:

• ne … pas = not
• ne … jamais = never

You don’t use pas together with jamais in standard French:

• Correct: Je ne la déplace jamais. = I never move it.
• Not standard: Je ne la déplace pas jamais. (double negative; sometimes heard in dialects, but not correct in standard French)

In informal spoken French, people very often drop ne:

• Je ne la déplace jamais. → formal / written / careful speech
• Je la déplace jamais. → very common in casual spoken French

For learning and writing, you should keep ne.
For understanding native speakers, expect to hear it dropped frequently.

Seul(e) here describes the subject (je), not la commode.

• If je is a man, you say:
  
  • Je ne la déplace jamais seul.
• If je is a woman, you say:
  
  • Je ne la déplace jamais seule.

So seul / seule agrees with the person who is alone, not with the object being moved.

Both can mean “alone / by myself”, but:

• seul = alone (neutral)
  
  • Je ne la déplace jamais seul. = I never move it alone.
• tout seul = “all alone / completely alone”, often a bit more emphatic or casual:
  
  • Je ne la déplace jamais tout seul.

In many everyday contexts, seul and tout seul are interchangeable in meaning; tout seul just sounds more colloquial or expressive.

Both can involve movement, but they’re not identical:

• déplacer = to move something from one place to another (change its position in space)
  
  • Je déplace la commode. = I move the chest of drawers to another spot.
• bouger = to move / to budge (more general movement, can be slight)
  
  • Ne bouge pas ! = Don’t move!
  • Je bouge la commode un peu. = I move/shift the chest of drawers a bit.

In this sentence, déplacer is natural because we’re talking about relocating a heavy piece of furniture.

In French, object pronouns usually go before the conjugated verb in simple tenses:

• je la déplace (I move it)
• je ne la déplace pas (I don’t move it)

The order is:

1. Subject: je
2. Negative part 1: ne
3. Object pronoun: la
4. Verb: déplace
5. Negative part 2 / adverbs: jamais, pas, etc.

So: je ne la déplace jamais is the standard word order.

Yes. That sentence is also correct:

• Je ne déplace jamais la commode seul.

Meaning is the same: you never move the chest of drawers alone.
The original sentence simply avoids repeating la commode by using the pronoun la.

The comma separates:

1. The cause: La commode est lourde
2. The consequence: alors je ne la déplace jamais seul

In English you might also separate them with a comma:
The chest of drawers is heavy, so I never move it by myself.

In French, using a comma here is normal and helps show the logical connection.

For this meaning (“by myself / alone”), seul normally goes after the verb phrase, as in the original:

• Je ne la déplace jamais seul.

Other positions would change the meaning or sound wrong. For example:

• Je seul ne la déplace jamais. → unnatural, and sounds like emphasis on me alone in a strange way.

So keep seul / seule after the verb phrase when it means “alone”.