אני נורא עייפה עכשיו, ולכן אני רוצה ללכת לישון מוקדם.

Because the speaker is female. In Hebrew, adjectives agree with the gender and number of the subject.

• אני עייף = I am tired said by a male
• אני עייפה = I am tired said by a female

So in this sentence, עייפה tells you the speaker is a woman or girl.

In Hebrew, the verb to be is usually omitted in the present tense.

So:

• אני עייפה literally looks like I tired
• but it means I am tired

This is completely normal Hebrew. In past and future, forms of to be can appear, but in present-tense sentences like this, they usually do not.

Here נורא means very, really, or terribly as an intensifier.

So:

• אני עייפה = I am tired
• אני נורא עייפה = I am really / מאוד tired

Originally נורא is related to awful or terrible, but in everyday speech it is very commonly used just to strengthen what follows.

It is a bit like saying I’m super tired.

לכן means therefore or so.
ולכן is simply and therefore / and so.

The ו־ at the beginning is the common Hebrew word for and.

So:

• לכן = therefore / so
• ולכן = and therefore / and so

In this sentence, ולכן smoothly connects the two clauses: I’m really tired now, and therefore I want to go to sleep early.

Hebrew often repeats the subject when starting a new clause, even if English might sometimes leave it out.

So this structure is very natural:

• אני נורא עייפה עכשיו, ולכן אני רוצה...

Literally:

• I am very tired now, and therefore I want...

The second אני helps make the clause complete and clear. Hebrew often prefers this kind of explicit subject.

This is a very common Hebrew structure:

• רוצה = want
• ללכת = to go
• לישון = to sleep

So literally it is:

• I want to go to sleep

Hebrew often uses רוצה + infinitive, just like English uses want to + verb.

The phrase ללכת לישון is a fixed everyday expression meaning to go to sleep or to go to bed.

Because Hebrew uses the expression ללכת לישון, literally to go to sleep.

It is made of:

• ללכת = to go
• לישון = to sleep

This works just like English to go to sleep. The first verb expresses movement into the action or state, and the second gives the action itself.

This is a very common pattern in Hebrew, not something unusual.

Because מוקדם here functions as an adverb, not as an adjective describing the speaker.

In this sentence, it means early in the sense of at an early time.

• לישון מוקדם = to sleep early / to go to sleep early

When Hebrew uses adjectives adverbially, it often uses the masculine singular form.

Compare:

• היא עייפה = She is tired → adjective agrees with she
• היא הולכת לישון מוקדם = She goes to sleep early → מוקדם describes when/how, so it stays in the common adverb-like form

The feminine singular form of רוצה is already רוצה.

The forms are:

• masculine singular: רוצה
• feminine singular: רוצה
• masculine plural: רוצים
• feminine plural: רוצות

So in writing, masculine singular and feminine singular are often the same with this verb in the present tense. You usually understand the gender from context or from nearby words like עייפה, which clearly shows the speaker is female.

Yes. You could say:

• אני מאוד עייפה עכשיו...

That would also mean I am very tired now.

The difference is mostly in tone:

• מאוד = neutral, standard very
• נורא = more colloquial, emotional, like really / super / terribly

Both are common, but נורא can sound a bit more expressive.

It can move. Hebrew word order is flexible, especially with time words like עכשיו.

For example, all of these are natural:

• אני נורא עייפה עכשיו
• עכשיו אני נורא עייפה
• אני עכשיו נורא עייפה

The exact position can slightly change emphasis, but the basic meaning stays the same.
In your sentence, putting עכשיו after עייפה sounds very natural.

Yes, but it is a little more formal or structured than some other connectors.

In everyday speech, people might also say:

• אז = so
• כי אז in some contexts
• just pause and continue without a formal connector

So this sentence is natural, but ולכן can sound slightly more written or careful than plain אז.

Compare:

• אני נורא עייפה עכשיו, ולכן אני רוצה ללכת לישון מוקדם.
• אני נורא עייפה עכשיו, אז אני רוצה ללכת לישון מוקדם.

Both are fine; the second is a bit more conversational.