Sem ajuda, eu não consigo mover a mesa.

Sem ajuda means without help.

In Portuguese, sem is the preposition without. Here, ajuda is being used in a general, uncountable sense, so Sem ajuda means without help / without any help.

You can also say sem a ajuda de alguém when you mean without someone’s help more specifically, for example:

• Sem a ajuda do João, eu não consigo mover a mesa.
  = Without João’s help, I can’t move the table.

So in your sentence, Sem ajuda is the natural general version.

Yes, eu can be omitted.

Portuguese often drops subject pronouns when the verb form already makes the subject clear. So these are both correct:

• Sem ajuda, eu não consigo mover a mesa.
• Sem ajuda, não consigo mover a mesa.

Both mean the same thing.

Including eu can add a little emphasis or clarity, especially in contrast with someone else:

• Tu consegues, mas eu não consigo.
  = You can manage it, but I can’t.

So eu is optional here, but perfectly natural.

Não consigo comes from the verb conseguir, which often means:

• to manage
• to be able to
• to succeed in

So não consigo mover a mesa means:

• I can’t move the table
• or more literally, I’m not able to manage to move the table

This is slightly different from just using não posso, which usually means I can’t in the sense of I’m not allowed to or it’s not possible for some reason.

Compare:

• Não consigo mover a mesa.
  = I can’t manage to move the table.
  (It’s too heavy, I’m not strong enough, etc.)

• Não posso mover a mesa.
  = I can’t move the table.
  (Maybe I’m not allowed to, or I must not.)

Yes. This is a very common point of confusion.

In eu não consigo, consigo is the 1st person singular form of the verb conseguir:

• eu consigo = I can / I manage

But consigo can also be a completely different word meaning with you in formal Portuguese:

• Vou consigo.
  = I’m coming with you.
  (formal you)

So in your sentence, consigo is definitely a verb, not a prepositional form. The structure makes that clear:

• eu não consigo mover...
  = subject + negation + verb + infinitive

Because after conseguir, Portuguese normally uses another verb in the infinitive.

So the pattern is:

• conseguir + infinitive

Examples:

• Consigo fazer isso.
  = I can manage to do that.
• Não conseguimos abrir a porta.
  = We can’t manage to open the door.
• Ela conseguiu terminar o trabalho.
  = She managed to finish the work.

So:

• não consigo mover a mesa
  literally = I don’t manage to move the table

Sometimes, yes, but they are not always identical.

Mover means to move in a direct, physical sense. It fits very naturally here:

• mover a mesa = move the table

Mexer can also sometimes mean to move, but it often has broader meanings like:

• to touch
• to fiddle with
• to stir
• to mess with
• to shift

In European Portuguese, mexer na mesa would usually sound more like touching/handling/messing with the table rather than clearly moving the table from one place to another.

So if you mean physically shifting the table, mover a mesa is the safest and clearest choice.

Portuguese often uses definite articles more than English does.

So where English might say:

• move the table

Portuguese says:

• mover a mesa

The article a means the, and mesa is a feminine noun.

In many situations, Portuguese sounds more natural with the article when referring to a specific object known in the context.

For example:

• Fecha a porta.
  = Close the door.
• Abre a janela.
  = Open the window.
• Move a mesa.
  = Move the table.

Saying just mover mesa would generally not be correct here.

The noun mesa is grammatically feminine, so it takes feminine articles and adjectives:

• a mesa = the table
• uma mesa = a table
• a mesa pesada = the heavy table

There is no universal rule that always tells you a noun’s gender, but nouns ending in -a are often feminine, and mesa is one of them.

You just need to learn it as part of the word:

• mesa → feminine

Yes. The sentence can be rearranged a little without changing the basic meaning.

Your sentence:

• Sem ajuda, eu não consigo mover a mesa.

Other natural possibilities include:

• Eu não consigo mover a mesa sem ajuda.
• Não consigo mover a mesa sem ajuda.

These all mean essentially the same thing.

Starting with Sem ajuda puts emphasis on the condition first: without help. That can sound slightly more dramatic or contrastive.

Putting sem ajuda at the end is also very natural and often feels more neutral in everyday speech.

No. Sem ajuda is not a full clause; it is a prepositional phrase.

It contains:

• sem = without
• ajuda = help

It works like an adverbial phrase, giving the condition or circumstance under which the action happens.

So the full sentence structure is roughly:

• Sem ajuda = adverbial phrase
• eu = subject
• não consigo = verb phrase
• mover a mesa = infinitive phrase / complement

This sentence sounds natural and neutral in everyday European Portuguese.

• Sem ajuda, eu não consigo mover a mesa.

It is not especially formal, and not especially slangy either. It would work in normal conversation.

In casual speech, a speaker might simply say:

• Não consigo mover a mesa sem ajuda.

That may sound a bit more spontaneous in everyday conversation, but your original version is absolutely normal.

In European Portuguese, não is pronounced roughly like nowng, but that is only an approximation.

A few useful points:

• the ão sound is nasal
• it does not sound like a plain English ow
• the final sound is not a fully pronounced n

So não has a nasal diphthong that English doesn’t really have exactly.

Also, in fast European Portuguese speech, unstressed words can be reduced quite a bit, but não usually remains clear because it is important for the meaning.

Yes, that is a good literal translation, and it helps show how the Portuguese works.

Word by word:

• Sem = without
• ajuda = help
• eu = I
• não = not
• consigo = manage / am able
• mover = to move
• a mesa = the table

But in natural English, you would normally say:

• Without help, I can’t move the table.
• I can’t move the table without help.

So the literal version is useful for understanding the grammar, but not the most natural final translation in English.