אני רוצה להחליף את הנעליים, כי המידה לא טובה.

After רוצה (want), Hebrew normally uses the infinitive, just like English uses to + verb.

• רוצה = want
• להחליף = to exchange / to replace

The ל־ at the beginning of להחליף is part of the infinitive form, so the whole phrase רוצה להחליף means want to exchange.

להחליף can mean to replace, to switch, or to exchange, depending on context.

In this sentence, because we are talking about shoes and size, it most naturally means to exchange or to replace with a different pair/size. In a store, אני רוצה להחליף את הנעליים is a very natural thing to say.

את is the marker of a definite direct object. It usually appears before a noun that is specific or already known, especially when it has ה־ (the).

So:

• הנעליים = the shoes
• את הנעליים = marks the shoes as the direct object of להחליף

English does not have a separate word for this, so את is usually not translated.

The prefix ה־ means the.

So:

• נעליים = shoes / a pair of shoes
• הנעליים = the shoes

Because the speaker means a specific pair of shoes, Hebrew uses הנעליים.

The ending ־יים is historically a dual ending, often used with things that come in pairs.

נעליים is the normal Hebrew word for shoes. Even though it has this dual-looking ending, in modern Hebrew it behaves like a plural noun.

For example:

• נעליים חדשות = new shoes

So a learner should usually just memorize נעליים as the standard word for shoes.

In the present tense, Hebrew verb forms like רוצה show gender and number, but not person.

So רוצה by itself could mean:

• I want
• you want
• he wants

Because of that, Hebrew often includes the subject pronoun in the present tense to make the meaning clear. So אני רוצה clearly means I want.

Yes. In normal Hebrew spelling, a male speaker and a female speaker would both write:

אני רוצה להחליף את הנעליים, כי המידה לא טובה.

The difference is in pronunciation:

• male: rotze
• female: rotza

Without vowel marks, the spelling is the same.

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

• טוב = masculine singular
• טובה = feminine singular

So:

• מידה טובה = a good size
• המידה לא טובה = the size is not good / not right

This is normal Hebrew adjective agreement.

לא is used to negate verbs and adjectives.

Here, טובה is an adjective, so Hebrew says:

• המידה לא טובה = the size is not good

אין is used more for there is/there are not or does not have.

So this sentence needs לא, not אין.

Here מידה means size, especially clothing or shoe size.

So המידה לא טובה literally means the size is not good, but in natural English it usually means something like:

• the size is wrong
• the size isn’t right
• it doesn’t fit properly

So the Hebrew is a little more literal than the most natural English translation.

Because the speaker is talking about the size of the pair. Even though the shoes are plural, the idea of size is treated as one thing.

So Hebrew says המידה = the size, singular.

This works the same way in English:

• The shoes are nice, but the size is wrong.

In this sentence, yes. כי means because and introduces the reason:

• אני רוצה להחליף את הנעליים = I want to exchange the shoes
• כי המידה לא טובה = because the size isn’t right

One extra note: כי can also mean that in some other sentences, but here it clearly means because.