El forro protege el contenido del bulto.

Because Spanish usually uses the definite article with nouns where English might also use the.

• el forro = the lining / the cover
• el contenido = the contents / the content

In this sentence, both nouns are specific, so el is used with each one.

Because de + el contracts to del in Spanish.

So:

• de el bulto → del bulto

This is a standard rule. The only common exception is when el is part of a proper name, such as de El Escorial.

Protege is the third-person singular present tense of proteger.

So it means:

• he/she/it protects
• the lining protects

The subject is el forro, which is singular, so the verb must also be singular:

• El forro protege... = The lining protects...

Because Spanish sentences normally use a conjugated verb, not the infinitive, as the main verb.

• proteger = to protect
• protege = protects

So:

• El forro protege... = correct
• El forro proteger... = incorrect

In this kind of sentence, forro usually means something like:

• lining
• inner layer
• protective cover

The exact translation depends on context. In Spain, forro can refer to the inside lining of something or a protective outer layer. Here, it is clearly something that protects what is inside.

Bulto can mean different things depending on context, such as:

• bundle
• package
• parcel
• bulky item

In this sentence, del bulto most naturally means of the package/bundle or inside the bundle.

So el contenido del bulto means the contents of the bundle/package.

Spanish often uses contenido as a singular collective noun, where English commonly uses contents in the plural.

So:

• el contenido = the content or the contents

Both ideas are possible in English, but Spanish commonly keeps it singular.

Because each of those nouns is grammatically masculine:

• el forro
• el contenido
• el bulto

That is why they all take el rather than la.

This is grammatical gender, which does not necessarily mean anything about biological sex. It is simply part of how the nouns are classified in Spanish.

It follows a very common Spanish pattern:

Subject + verb + object

• El forro = subject
• protege = verb
• el contenido del bulto = direct object

Inside the object:

• el contenido = the content
• del bulto = of the bundle/package

So the sentence is built very straightforwardly.

It describes contenido, not the verb.

So the meaning is:

• the content of the bundle

not

• protects by/from the bundle

In other words, del bulto tells you which content we are talking about.

Normally, no. In this sentence, the articles sound natural and expected:

• El forro protege el contenido del bulto.

Leaving them out would sound unnatural in standard Spanish:

• Forro protege contenido del bulto. → not natural

Spanish generally uses articles more often than English learners sometimes expect.

No. In protege, the g is pronounced like the Spanish sound in gente, not like the English g in go.

In Spain, it sounds roughly like this:

• pro-TE-he

Also useful pronunciation notes:

• forro has a strong rr sound
• bulto has a clear l and t
• del is short and unstressed

So a rough guide would be:

el FO-rro pro-TE-he el kon-te-NI-do del BUL-to

That is only an approximation, but it helps show the main sounds.