Dubito che il check-out richieda più di cinque minuti.

Because dubitare che + clause is the normal pattern when you are expressing doubt about a whole statement.

• Dubito che il check-out richieda più di cinque minuti = I doubt that check-out takes more than five minutes.

By contrast, dubitare di is usually followed by:

• a noun: Dubito di lui = I doubt him / I have doubts about him
• an infinitive in some contexts: Dubito di riuscire = I doubt I’ll manage

So here, since the speaker is doubting a full idea (that check-out takes more than five minutes), che is the natural choice.

Because after dubito che, Italian normally uses the subjunctive.

• richiede = indicative present
• richieda = subjunctive present

Expressions of doubt, uncertainty, opinion, emotion, or possibility often trigger the subjunctive in Italian. Since dubito expresses doubt, the verb in the following clause goes into the subjunctive:

• Dubito che... richieda...

This is one of the most important things to notice in the sentence.

Richieda is the present subjunctive, third person singular, of richiedere (to require, take, call for).

Here is the present subjunctive of richiedere:

• che io richieda
• che tu richieda
• che lui/lei richieda
• che noi richiediamo
• che voi richiediate
• che loro richiedano

In this sentence, the subject is il check-out, which is singular, so you need richieda.

In Italian, nouns are normally used with an article much more often than in English.

So:

• il check-out
• il computer
• il bar
• lo shopping

Even when the noun is borrowed from English, Italian usually treats it like a normal noun and gives it an article.

Here, check-out is masculine singular, so il is used:

• il check-out

Yes, check-out is used in Italian, especially in contexts like hotels, airports, and online purchases. Its exact meaning depends on context.

In this sentence, il check-out most naturally suggests:

• the hotel departure procedure, or
• the final payment/completion stage

Italian also sometimes uses more native alternatives depending on the situation, but check-out is very common and understandable.

Because più di is the normal way to express more than before a number or quantity.

• più di cinque minuti = more than five minutes
• più di due ore = more than two hours
• più di cento euro = more than one hundred euros

A useful contrast:

• più di is often used before numbers, quantities, nouns, infinitives
• più che is often used when comparing clauses or emphasizing contrast

So in this sentence, più di cinque minuti is exactly what you would expect.

In standard Italian, that would generally be considered incorrect, because dubitare che normally requires the subjunctive.

So the standard version is:

• Dubito che il check-out richieda più di cinque minuti.

You may sometimes hear non-standard or less careful spoken Italian where the indicative appears after structures that traditionally require the subjunctive, but for a learner, you should definitely use richieda here.

The subject is il check-out.

So the sentence structure is:

• Dubito = I doubt
• che = that
• il check-out = subject of the subordinate clause
• richieda = verb
• più di cinque minuti = object/complement expressing amount of time

In other words, it is the check-out that is supposedly taking or requiring more than five minutes.

It can mean both, depending on context.

Literally:

• richiedere = to require

But with time expressions, it often translates naturally as:

• to take

So:

• Il check-out richiede cinque minuti
  can mean
  Check-out takes five minutes

This is very common in Italian: a verb may be translated less literally in English to sound natural.

Because Italian often uses the present tense for general statements, current situations, or what is expected to happen.

Here the sentence means something like:

• I doubt that check-out takes more than five minutes
• I doubt that check-out would take more than five minutes (depending on context)

The Italian present can cover ideas that English might sometimes express with the present simple or with a slightly more contextual translation.

Yes, it usually sounds fairly definite: the speaker is saying they think something is unlikely or not true.

• Dubito che il check-out richieda più di cinque minuti
  = I doubt that check-out takes more than five minutes.

It does not mean the speaker is 100% certain, but it clearly shows skepticism.

If you wanted to sound softer, Italian offers other possibilities, for example:

• Non credo che... = I don’t think that...
• Mi sembra difficile che... = It seems unlikely that...

All of these also commonly take the subjunctive.

A rough pronunciation guide is:

DOO-bee-to kay eel chek-OUT ree-KYEH-da pyoo dee CHEEN-kweh mee-NOO-tee

A few points:

• Dubito stress: DUbito
• che sounds like keh
• più sounds like pyoo
• cinque sounds roughly like CHEEN-kweh
• richieda has the stress on -chie-: ri-CHIE-da

Also, check-out in Italian is usually pronounced in an Italian-influenced way, but the English origin is still clear.