Protejăm lustra cu folia cu bule.

Because Romanian often drops the subject pronoun when it is clear from the verb form.
Protejăm already tells you the subject is we.

• protejez = I protect
• protejezi = you protect
• protejăm = we protect

So Noi protejăm lustra... is possible, but noi is usually unnecessary unless you want emphasis.

Protejăm is the present tense, 1st person plural form of the verb a proteja = to protect.

In English, it can correspond to either:

• we protect
• we are protecting

Romanian does not normally use a separate progressive form like English are protecting. The context tells you whether the action is habitual or happening right now.

In Romanian, the definite article is usually attached to the end of the noun, not written as a separate word.

So here:

• lustră = a chandelier
• lustra = the chandelier

and

• folie = a sheet/film
• folia = the sheet/the film

That is why you do not see a separate word like English the.

Because lustră is the indefinite form, while lustra is the definite form.

For many feminine nouns ending in -ă, the final -ă changes when the definite article is added:

• lustră = a chandelier
• lustra = the chandelier

So this is not a spelling mistake. It is the normal way the noun changes when it becomes definite.

For the same reason: folia is the definite form of folie.

• folie = a film / a sheet / a plastic sheet
• folia = the film / the sheet

In this sentence, the speaker is referring to a specific material being used, so the definite form sounds natural.

Because the two cu phrases do different jobs.

• cu folia cu bule: the first cu means with / using
• inside folia cu bule: the second cu means with, describing the type of film: film with bubbles

So literally the structure is:

We protect the chandelier with the film with bubbles.

That may sound repetitive in English, but it is completely normal in Romanian.

Because cu bule is describing the kind of material, not referring to some specific bubbles.

• bulă = bubble
• bule = bubbles
• bulele = the bubbles

In folie cu bule, the noun stays indefinite because the phrase means something like film with bubbles as a type of product. This is the normal Romanian expression for bubble wrap.

Yes. Folie cu bule is the standard Romanian expression for bubble wrap.

Literally, it means film/plastic sheet with bubbles.

So:

• folie cu bule = bubble wrap
• folia cu bule = the bubble wrap

Because pe is usually used before direct objects that are people, or in some special emphatic situations.

Here, lustra is an inanimate object and an ordinary direct object, so pe is not needed.

Compare:

• Văd fata. = I see the girl.
• Îl văd pe Andrei. = I see Andrei.

In your sentence, lustra is just the direct object of protejăm.

Yes. Romanian word order is more flexible than English word order.

The neutral order here is:

Protejăm lustra cu folia cu bule.

But other orders are possible for emphasis, for example:

• Cu folia cu bule protejăm lustra.
  Emphasizes the material being used.

Even so, the original version sounds very natural and straightforward.

A useful breakdown is:

• Protejăm = verb: we protect / we are protecting
• lustra = direct object: the chandelier
• cu folia cu bule = prepositional phrase: with the bubble wrap

So the structure is:

Verb + direct object + instrument

That is a very common and natural Romanian pattern.