أضع ملابسي على الكرسي أمام السرير عندما أعود إلى البيت.

Because the verb already includes the subject.

• أضع = I put
• أعود = I return / I come back

In the present tense, the prefix أ- marks first person singular. So Arabic does not need أنا here.

You can say أنا أضع ملابسي..., but that usually adds emphasis, like I put my clothes...

Starting with the verb is very normal in Arabic. This makes the sentence a verbal sentence.

So:

• أضع ملابسي... = a very natural MSA structure
• أنا أضع ملابسي... = also possible, but it gives more prominence to I

English usually needs an explicit subject first, but Arabic often does not.

أضع is the present-tense form of the verb وضع.

Its basic meaning is to put, to place, or to set down.

So here أضع ملابسي على الكرسي means I put / place my clothes on the chair.

Grammatically:

• past: وضعَ = he put
• present: يضعُ = he puts
• present, 1st person singular: أضعُ = I put

It is made of two parts:

• ملابس = clothes
• -ي = my

So:

• ملابس = clothes
• ملابسي = my clothes

This -ي is a possessive suffix attached directly to the noun.

It is plural.

In normal usage, ملابس means clothes. Even though English clothes is also plural in meaning, it is useful to remember that Arabic treats this as a plural noun too.

So ملابسي is literally my clothes, not my clothing item.

Because the -ي suffix hides it.

Functionally, ملابسي is the direct object of أضع, so it is accusative in grammar. But when a noun has the suffix -ي meaning my, the usual case ending is not clearly visible in the normal written form.

So learners should understand:

• function: direct object
• case: accusative
• visible form: ملابسي stays the same in ordinary spelling

على is the preposition meaning on or on top of.

So:

• على الكرسي = on the chair

After a preposition like على, the following noun is genitive in grammar.

Also, الكرسي is definite because it means the chair, probably a specific chair known from the context.

If you said على كرسي instead, that would mean on a chair.

They are pronounced differently because of moon letters and sun letters.

• الكرسي → al-kursī
  ك is a moon letter, so the l sound of ال is pronounced.

• السرير → as-sarīr
  س is a sun letter, so the l sound is not pronounced, and the s is doubled in pronunciation.

This is why Arabic spelling stays the same, but pronunciation changes.

أمام means in front of.

In grammar, it is often described as a noun of place / ظرف مكان rather than a simple preposition in the English sense.

In أمام السرير:

• أمام = in front
• السرير = the bed

Together: in front of the bed

The noun after أمام is in the genitive because this structure works like an iḍāfa-type relation.

عندما is a common MSA word meaning when. It introduces a time clause.

So:

• عندما أعود إلى البيت = when I return home

A few useful points:

• It is very normal to follow عندما with a present-tense verb.
• You do not put أن after it here.
• Other words such as حين can also mean when, but عندما is very standard and clear.

Because the sentence expresses a habitual/repeated action.

It means something like:

• I put my clothes on the chair in front of the bed when I come back home
• or Whenever I return home, I put my clothes...

In Arabic, the present tense is often used for actions that are habitual, regular, or generally true.

So this is not necessarily about right now. It is about what the speaker usually does.

Yes. In context, البيت often means home, not just the house in a literal architectural sense.

So:

• أعود إلى البيت = I return home

The preposition إلى means to.

In careful MSA, عاد normally goes with إلى when you say return to a place:

• عاد إلى البيت = he returned home
• أعود إلى البيت = I return home

You could also use المنزل, but البيت is extremely common.

Yes, absolutely.

You can say:

• أضع ملابسي على الكرسي أمام السرير عندما أعود إلى البيت.
• عندما أعود إلى البيت، أضع ملابسي على الكرسي أمام السرير.

Both are correct.

The second version gives a little more emphasis to the time setting: When I return home, ...

Arabic allows this kind of flexibility more easily than English learners sometimes expect.