קשה לי להבחין בין שתי המילים האלה כשאני קורא מהר.

Literally, קשה לי means hard/difficult to me.

This is a very common Hebrew pattern:

• קשה לי = it is difficult for me
• קל לי = it is easy for me
• נעים לי = it is pleasant for me

So instead of building the idea around I, Hebrew often builds it around the situation:

• קשה לי להבחין... = It’s difficult for me to distinguish...

That is why לי (to me / for me) appears instead of a subject like אני.

After expressions like קשה לי or קל לי, Hebrew usually uses an infinitive to say what is difficult or easy.

So:

• קשה לי להבחין = It’s hard for me to distinguish
• קל לי להבין = It’s easy for me to understand
• קשה לי לזכור = It’s hard for me to remember

Here, להבחין means to distinguish / to tell apart / to notice the difference.

In this sentence, להבחין בין... means to distinguish between... or to tell apart....

So:

• להבחין בין שתי המילים האלה = to distinguish between these two words

Depending on context, להבחין can also mean to notice, but with בין it strongly suggests distinguishing between two things.

בין means between. In this sentence, the speaker is not naming two separate words one by one; they are referring to them as a pair:

• בין שתי המילים האלה = between these two words

So Hebrew does not need a separate and here.

If you named the two items individually, you would often see a structure like:

• בין X ל-Y = between X and Y

But when you say between these two words, one בין is enough.

Because שתי is the form used before a feminine noun.

Compare:

• שתיים = two when the number stands alone
• שתי מילים = two words

This is a normal Hebrew pattern:

• שני ספרים = two books
• שתי מילים = two words

So in front of a noun, Hebrew uses שני / שתי, not שניים / שתיים.

Because מילה (word) is a feminine noun, and its plural מילים is also feminine.

This is one of those things that can confuse learners: the ending -ים often looks masculine, but not always. Some feminine nouns have plural forms in -ים.

So:

• singular: מילה = word (feminine)
• plural: מילים = words (still feminine)

That is why Hebrew uses:

• שתי מילים not
• שני מילים

In Hebrew, demonstratives like this / these usually come after the noun.

So:

• המילים האלה = these words
• הספר הזה = this book
• הילדים האלה = these children

This is the normal Hebrew word order.

Also notice that both parts are definite:

• המילים = the words
• האלה = these

So Hebrew literally says something like the words these.

כשאני means when I.

It is made from:

• כש־ = when
• אני = I

So:

• כשאני קורא = when I read / when I am reading

You can think of כש־ as a shortened, very common spoken/written form of כאשר.

Examples:

• כשאני עייף, אני שותה קפה. = When I’m tired, I drink coffee.
• כשאני קורא מהר... = When I read quickly...

Because קורא is the masculine singular present-tense form.

So this sentence sounds as if the speaker is male.

• אני קורא = I read / I am reading (male speaker)
• אני קוראת = I read / I am reading (female speaker)

If the speaker were female, the sentence would be:

• קשה לי להבחין בין שתי המילים האלה כשאני קוראת מהר.

It can mean either, depending on context.

Hebrew present tense often covers both:

• I read
• I am reading

So כשאני קורא מהר can mean:

• when I read quickly
• when I’m reading quickly

In this sentence, the general meaning is probably habitual or general: when I read fast.

מהר means quickly / fast.

Here it modifies קורא:

• קורא מהר = read(s) quickly

Putting it after the verb is very natural in Hebrew.

Examples:

• הוא מדבר מהר. = He speaks fast.
• אני כותב מהר. = I write quickly.
• כשאני קורא מהר... = when I read quickly...

A helpful breakdown is:

• קשה = difficult / hard
• לי = to me / for me
• להבחין = to distinguish
• בין = between
• שתי = two (feminine form before a noun)
• המילים = the words
• האלה = these
• כשאני = when I
• קורא = read / am reading (masculine singular)
• מהר = quickly / fast

So the structure is roughly:

Hard for me to distinguish between these two words when I read quickly.

A simple transliteration is:

kashe li lehavkhin bein shtei ha-milim ha-ele kshe-ani kore maher

A few pronunciation notes:

• קשה = ka-SHE
• להבחין = le-hav-KHIN
  The kh sound is the throaty sound of ח / כ.
• שתי = shtei
• כשאני = kshe-ani
• קורא = ko-RE
• מהר = ma-HER

If spoken naturally, the sentence flows pretty smoothly as one unit.