Когда мясо хорошо замариновано, шашлык получается мягче и ароматнее.

Because the sentence begins with a subordinate clause introduced by когда (when):

• Когда мясо хорошо замариновано = When the meat is well marinated
• шашлык получается мягче и ароматнее = the shashlik turns out softer and more aromatic

In Russian, a subordinate clause is normally separated from the main clause by a comma.

Когда means when, while если means if.

Here, когда presents this as a regular relationship or general fact:

• Когда мясо хорошо замариновано, шашлык получается мягче и ароматнее. = When meat is well marinated, shashlik turns out softer and more aromatic.

If you used если, the meaning would be a bit more conditional:

• Если мясо хорошо замариновано, шашлык получится мягче и ароматнее. = If the meat is well marinated, the shashlik will turn out softer and more aromatic.

So когда sounds more like a general cooking truth.

Замариновано is the short-form passive participle of замариновать (to marinate, perfective).

It means something like:

• has been marinated
• is marinated in the sense of a completed result

So:

• мясо хорошо замариновано = the meat is well marinated / has been well marinated

This short form is commonly used in Russian to describe a state resulting from an action.

Compare:

• замаринованное мясо = marinated meat
  This is the full form, used like an adjective before a noun.
• мясо замариновано = the meat is marinated
  This is the short form, used as the predicate.

Because хорошо here is an adverb, and it modifies the participle/state замариновано.

It answers the question how?

• хорошо замариновано = well marinated

You would not use an adjective like хорошее here, because that would need to describe a noun, not the action/result.

Compare:

• хорошее мясо = good meat
  (хорошее describes мясо)
• мясо хорошо замариновано = the meat is well marinated
  (хорошо describes замариновано)

Because мясо is the subject of the subordinate clause:

• мясо ... замариновано = the meat is marinated

Even though English often uses a structure with is, Russian still treats мясо as the grammatical subject, so it stays in the nominative.

The same is true for шашлык in the main clause:

• шашлык получается... = the shashlik turns out...

So this sentence actually has two subjects:

• мясо in the first clause
• шашлык in the second clause

Получаться often means to turn out, to come out, or to end up being.

In cooking contexts, it is very common:

• Суп получился вкусным. = The soup turned out tasty.
• Пирог получается сухим. = The pie comes out dry.

So here:

• шашлык получается мягче и ароматнее
  = the shashlik turns out softer and more aromatic

It does not literally mean is received here. It means the final result has those qualities.

Russian often uses the present tense of the imperfective to express a general rule, habitual result, or what usually happens.

So:

• шашлык получается мягче и ароматнее means something like shashlik turns out softer and more aromatic / will generally come out softer and more aromatic

If you wanted to talk about one specific future result, you might use the perfective future:

• шашлык получится мягче и ароматнее = the shashlik will turn out softer and more aromatic

In your sentence, the present tense sounds like a general cooking principle.

Мягче and ароматнее are the normal comparative forms of the adjectives:

• мягкий → мягче = softer
• ароматный → ароматнее = more aromatic

Russian often prefers these short comparative forms in everyday speech and writing.

So:

• шашлык получается мягче и ароматнее
  = the shashlik turns out softer and more aromatic

You could also say:

• более мягкий
• более ароматный

But that is usually more formal, heavier, or less natural here.

Russian often leaves the comparison implicit when it is obvious from context.

So мягче и ароматнее means:

• softer and more aromatic
  than it would otherwise be
• or softer and more aromatic
  than non-marinated meat/shashlik

English can do this too:

• This version is better.
• It comes out softer.

Russian does not need to say чем... (than...) if the comparison is understood.

If you wanted to make it explicit, you could say something like:

• ...мягче и ароматнее, чем без маринада. = ...softer and more aromatic than without marinade.

Russian has no articles.

So words like the meat, a shashlik, or the shashlik are understood from context.

In this sentence:

• мясо can mean meat or the meat
• шашлык can mean shashlik or the shashlik

English needs articles; Russian does not.

Yes, Russian word order is fairly flexible, though the original version is the most neutral and natural.

Original:

• Когда мясо хорошо замариновано, шашлык получается мягче и ароматнее.

You could also say:

• Шашлык получается мягче и ароматнее, когда мясо хорошо замариновано.

This still means the same thing, but the focus shifts slightly. The original sentence puts the condition first, which feels very natural in explanations and recipes.

Usually, замариновано is the more natural choice here.

Why?

• замариновать is perfective and emphasizes a completed result
• замариновано therefore means has been marinated / is fully marinated

That fits this sentence well, because the important idea is the finished state of the meat before cooking.

Using мариновано is much less common and generally sounds less natural in this context.

This is a very common question.

• замариновано = short form
• замаринованное = full form

They are used differently:

1. Short form: used as part of the predicate

   • Мясо замариновано.
     = The meat is marinated.

2. Full form: used like an adjective before a noun

   • замаринованное мясо
     = marinated meat

So in your sentence, замариновано is correct because it is describing the state of the meat in a full clause.

Yes, it means the same basic thing: more aromatic.

• ароматный → ароматнее
• более ароматный = a longer analytical comparative

Ароматнее is completely normal and natural. Russian often forms comparatives this way, even when the English translation needs two words.

Similar examples:

• вкусный → вкуснее = tastier
• интересный → интереснее = more interesting
• полезный → полезнее = healthier / more useful

So мягче и ароматнее is a very natural pair.

Because получается adds the idea of the result of cooking/preparing, not just a simple state.

Compare:

• Шашлык будет мягче и ароматнее. = The shashlik will be softer and more aromatic.

• Шашлык получается мягче и ароматнее. = The shashlik turns out softer and more aromatic.

The second version sounds more idiomatic in cooking advice because it focuses on how the dish comes out in the end.

It can be understood either way depending on context, but without more context it usually sounds like a general statement:

• When meat is well marinated, shashlik turns out softer and more aromatic.

Russian often uses singular nouns like мясо and шашлык to talk about things in general.

So the sentence is best understood as a general cooking observation, not necessarily as a comment about one particular batch.