Рабочая нагрузка слишком высокая.

Because нагрузка is a feminine singular noun, and the adjective has to agree with it.

• нагрузка = feminine
• so the adjective must also be feminine singular: высокая

Compare:

• высокий уровень = a high level (masculine)
• высокая нагрузка = a high workload/load (feminine)
• высокое давление = high pressure (neuter)

The same applies to рабочая, which also agrees with нагрузка.

For the same reason: рабочая describes нагрузка, and adjectives in Russian agree with the noun in gender, number, and case.

So here we get:

• рабочая = feminine singular nominative
• нагрузка = feminine singular nominative
• высокая = feminine singular nominative

Literally, this is something like work-related load is too high.

Рабочая нагрузка means workload or work burden.

It is a normal Russian phrase for:

• the amount of work someone has
• how heavy someone’s work responsibilities are

Depending on context, it can refer to:

• an employee’s workload
• a teacher’s workload
• a student’s academic load in some contexts, though there are other phrases for that too

So нагрузка by itself is load/burden, and рабочая narrows it to work-related.

In the present tense, Russian usually does not use a verb corresponding to English is/am/are.

So:

• Рабочая нагрузка слишком высокая. literally follows the pattern
• Workload too high.

But in natural English, we say The workload is too high.

This is completely normal in Russian:

• Он дома. = He is at home.
• Она занята. = She is busy.
• Проблема серьёзная. = The problem is serious.

In past or future tense, Russian does use forms of быть:

• Рабочая нагрузка была слишком высокой. = The workload was too high.
• Рабочая нагрузка будет слишком высокой. = The workload will be too high.

No. Слишком means too, not just very.

So:

• слишком высокая = too high
• очень высокая = very high

That distinction is important:

• очень simply strengthens the adjective
• слишком suggests more than is acceptable/desirable

Compare:

• Нагрузка очень высокая. = The workload is very high.
• Нагрузка слишком высокая. = The workload is too high.

Yes, Russian often uses высокий / высокая / высокое with abstract nouns in much the same way English uses high.

Examples:

• высокая температура = high temperature
• высокий уровень стресса = a high stress level
• высокая нагрузка = high workload/load

So even though высокий literally means high/tall, it also works naturally with things like levels, rates, pressure, workload, and intensity.

They are in the nominative case.

That is because the sentence has the structure:

• Рабочая нагрузка = the subject
• слишком высокая = the description/predicate adjective

So:

• рабочая — nominative feminine singular
• нагрузка — nominative feminine singular
• высокая — nominative feminine singular

In this kind of present-tense sentence, Russian commonly uses the nominative for both the subject and the adjective describing it.

Yes. That is also correct.

There are two common patterns here:

• нагрузка слишком высокая
• нагрузка слишком высока

The difference is mainly stylistic:

• высокая is the full form adjective and sounds more neutral/common in everyday speech
• высока is the short form adjective and can sound a bit more formal, written, or concise

Both mean essentially the same thing here:

• The workload is too high

Learners will usually hear and use the full form more often at first.

No, Russian word order is fairly flexible, but the neutral order here is:

• Рабочая нагрузка слишком высокая.

You may also see:

• Слишком высокая рабочая нагрузка.
  This sounds more like an excessively high workload as a noun phrase, or it can be used for emphasis.
• Рабочая нагрузка высокая.
  Without слишком, it just means The workload is high.

Changing word order often changes emphasis more than core meaning.

Russian has no articles like a/an/the.

So Рабочая нагрузка can mean:

• a workload
• the workload
• workload

The exact meaning depends on context.

In this sentence, English usually wants the workload is too high, but Russian simply says:

• Рабочая нагрузка слишком высокая.

Context tells you whether it is a specific workload or workload in general.

The stress is:

• рабо́чая нагру́зка сли́шком высо́кая

A rough pronunciation guide for English speakers:

• рабо́чая ≈ ra-BO-cha-ya
• нагру́зка ≈ na-GROO-ska
• сли́шком ≈ SLEESH-kam
• высо́кая ≈ vi-SO-ka-ya

A few helpful notes:

• Unstressed о is often pronounced more like a.
• я at the end of рабочая and высокая is pronounced as part of a two-syllable ending: -ая.
• груз in нагрузка has a clear z sound before к shifts it slightly, but learners can safely say na-GROO-ska.

Yes. Нагрузка is a broad word meaning load, strain, or burden, depending on context.

It can be used for:

• physical load: weight or pressure
• technical load: system load, electrical load
• mental or physical strain
• workload

Examples:

• физическая нагрузка = physical exertion
• учебная нагрузка = academic load
• нагрузка на сервер = load on the server
• рабочая нагрузка = workload

So the adjective before нагрузка is very important for clarifying the type of load.

Yes, if the context already makes it clear what kind of load you mean.

• Нагрузка слишком высокая. = The load/workload is too high.

This can sound natural when everyone already knows you are talking about work. But without context, нагрузка is broader and could mean other kinds of load or strain.

If you want to be specific, рабочая нагрузка is better.