La portada de esa revista es muy bonita.

With revista, portada means the cover, especially the front cover.

A few useful distinctions:

• portada = cover / front page
• with a magazine or book, it usually means the cover
• with a newspaper, it can also mean the front page

So in this sentence, la portada de esa revista is naturally understood as the cover of that magazine.

Spanish normally expresses this idea with:

noun + de + noun

So:

• la portada de esa revista = the cover of that magazine

This is much more natural in Spanish than trying to copy the English apostrophe structure.

You could sometimes use su portada for its cover, but that can be less clear, because su can mean his, her, its, your, or their depending on context.

These are all demonstratives, and they depend on distance or perspective:

• esta revista = this magazine
• esa revista = that magazine
• aquella revista = that magazine over there / that one further away

In your sentence, esa is the normal choice for that.

Also, esa has to match revista, which is feminine singular.

Because revista is a feminine singular noun.

Demonstratives must agree with the noun they describe:

• este libro
• esta revista
• ese libro
• esa revista

So:

• revista → feminine singular
• therefore → esa revista

Because esa already works as a determiner, like that in English.

In normal Spanish, you do not combine a definite article with a demonstrative in this kind of phrase.

So:

• de esa revista = correct
• de la esa revista = not normal Spanish

Compare:

• la revista = the magazine
• esa revista = that magazine

You choose one determiner, not both.

Spanish usually uses ser for more general or defining descriptions, and estar for states or conditions.

Here, es muy bonita describes the cover as having the quality of being beautiful, so ser is the normal choice.

• La portada es muy bonita. = The cover is very beautiful / pretty.

If you said está muy bonita, it could sound more like:

• it looks very nice right now
• it has turned out nicely
• it is looking especially nice in this moment or situation

So es is the most neutral and expected form here.

Because it agrees with portada, which is feminine singular.

In Spanish, adjectives usually agree in gender and number with the noun they describe.

Examples:

• el libro es bonito
• la revista es bonita
• los libros son bonitos
• las revistas son bonitas

Here:

• portada = feminine singular
• so the adjective must be bonita

Because muy is used before adjectives and adverbs.

• muy bonita = very beautiful
• muy interesante = very interesting

Mucho is used in other situations, such as with nouns or verbs:

• mucho dinero = a lot of money
• trabaja mucho = he/she works a lot

So in this sentence, muy bonita is the correct form.

Yes, in a normal sentence, la is the natural choice.

Spanish uses definite articles more often than English does. Here, la portada refers to a specific cover: the cover of that magazine.

• La portada de esa revista es muy bonita. = normal
• Portada de esa revista... = sounds incomplete, like a note, label, or headline

So in standard speech, keep la.

The standard, neutral order is:

La portada de esa revista es muy bonita.

That is the most natural version for everyday Spanish.

You can change the order for emphasis, but it becomes less neutral, for example:

• Muy bonita es la portada de esa revista.

That sounds more literary, dramatic, or marked.

So if you are learning the basic pattern, it is best to keep:

• subject + verb + adjective

In Spain, portada is the normal word here.

For magazines, newspapers, books, and similar things:

• portada = cover / front page

Tapa usually means:

• a lid
• a top
• sometimes a cover in other contexts

But for a magazine cover, portada is the most natural word.

So:

• La portada de esa revista... = exactly what a learner should use

A simple pronunciation guide would be:

la por-TA-da de EH-sa re-BIS-ta es muy bo-NI-ta

A few notes:

• revista: the v sounds very similar to a soft b in Spanish
• muy sounds roughly like mwee
• stress falls on:
  • porTAda
  • reBISta
  • boNIta

So the rhythm is:

La porTAda de EHsa reBISta es muy boNIta.