Tuj kiam ili malfermos la bankejon, ni deponos monon.

Because Esperanto often uses the future in both clauses when both actions are still in the future.

• malfermos = will open
• deponos = will deposit

So:

• Tuj kiam ili malfermos la bankejon, ni deponos monon.
• Literally: As soon as they will open the bank, we will deposit money.

In natural English, the first verb is usually present tense: As soon as they open the bank, we will deposit money.
But in Esperanto, using -os in both parts is completely normal.

Tuj kiam means as soon as or immediately when.

• tuj = immediately, right away
• kiam = when

Together they form a very common expression:

• tuj kiam = as soon as

So the sentence is talking about something that will happen immediately after the bank opens.

Bankejo emphasizes the place or premises of the bank.

Here is the breakdown:

• bank- = bank
• -ej- = place meant for something
• -o = noun ending

So:

• banko = a bank
• bankejo = a bank building, bank office, bank branch, bank premises

In many contexts, banko would also be understandable, but bankejo makes it especially clear that we mean the physical place that opens.

Because it is the direct object of malfermos.

• malfermi = to open
• You open something
• That something takes the accusative -n

So:

• ili malfermos la bankejon = they will open the bank

The -n here is not showing movement; it is simply marking the direct object.

For the same reason: it is the direct object of deponos.

• deponi = to deposit
• You deposit something
• Here, that something is mono → monon

So:

• ni deponos monon = we will deposit money

Again, this is ordinary accusative marking for the object of the verb.

Because la bankejon refers to a specific bank, while monon is nonspecific.

• la bankejon = the bank / the bank premises
• monon = money, not a specific previously identified pile of money

If you said la monon, it would mean the money, referring to specific money already known in the conversation.

So this sentence suggests:

• a specific bank
• an unspecified amount of money

Ili means they. In this sentence, it probably refers to the people who open the bank, such as:

• the bank staff
• the employees
• the management
• the people in charge

Esperanto uses ili just like English uses they when the exact people are not named but are understood from context.

Yes. This is a very common Esperanto pattern.

• fermi = to close
• malfermi = to open

The prefix mal- gives the opposite meaning.

Examples:

• bona = good → malbona = bad
• granda = big → malgranda = small
• fermita = closed → malfermita = open

So malfermos literally means will un-close, but in normal English we simply say will open.

Yes. Esperanto word order is fairly flexible, because the endings show the grammar clearly.

For example, these are also natural:

• Ni deponos monon tuj kiam ili malfermos la bankejon.
• Tuj kiam ili malfermos la bankejon, monon ni deponos.
  (more marked or stylistic)

The most neutral version is the original one:

• Tuj kiam ili malfermos la bankejon, ni deponos monon.

It starts with the time clause, which is very natural in both Esperanto and English.

The comma separates the subordinate time clause from the main clause.

• Tuj kiam ili malfermos la bankejon = subordinate clause
• ni deponos monon = main clause

So the comma helps show the structure clearly. Esperanto often uses commas quite regularly before or after subordinate clauses.

Deponi monon means to deposit money.

It is the normal verb for putting money into a bank account or placing something in deposit.

• deponi = deposit
• monon = money

So ni deponos monon means we will deposit money.

In context, the place is understood from the first clause, so Esperanto does not need to repeat in the bank unless you want to be extra explicit.

No, not in this sentence.

With malfermi, the thing being opened is the direct object, so you say:

• malfermi la bankejon = open the bank

If you said en la bankejon, that would mean into the bank, which would express movement into it, not the thing being opened.

So:

• correct: ili malfermos la bankejon
• not correct here: ili malfermos en la bankejon

Not always, but bankejo is often more precise.

• banko can mean the bank as an institution
• bankejo clearly points to the physical location or branch

In everyday usage, people may use either depending on style and context. But in a sentence about opening the premises, bankejo is especially neat and clear.

Yes, but the meaning changes slightly.

• kiam = when
• tuj kiam = as soon as

Compare:

• Kiam ili malfermos la bankejon, ni deponos monon.
  = When they open the bank, we will deposit money.
• Tuj kiam ili malfermos la bankejon, ni deponos monon.
  = As soon as they open the bank, we will deposit money.

The version with tuj gives a stronger sense of immediacy.