يفتح صديقي القفل الرقمي بدون مفتاح.

Because Arabic very often uses verb–subject–object order, especially in Modern Standard Arabic.

So this sentence is:

• يفتح = opens / is opening
• صديقي = my friend
• القفل الرقمي = the digital lock

A more literal order is: Opens my friend the digital lock without a key.

Arabic can also say:

• صديقي يفتح القفل الرقمي بدون مفتاح

That is more like My friend opens..., with extra emphasis on my friend.

يفتح is in the imperfect form, which commonly covers:

• present: opens
• ongoing present: is opening
• sometimes future, if the context makes that clear

In this sentence, without any future marker, it is usually understood as opens or is opening.

The basic form is:

• فتح = he opened
• يفتح = he opens / is opening

Because the subject is third person masculine singular: صديقي = my friend.

The form يفتح means he opens.

Arabic imperfect verbs change according to the subject. For example:

• يفتح = he opens
• تفتح = she opens
• أفتح = I open
• نفتح = we open

Since friend here is masculine singular, يفتح is the correct form.

صديقي means my friend.

It is made from:

• صديق = friend
• ـي = my

So:

• صديق = a friend / friend
• صديقي = my friend

That final ـي is a possessive suffix. Arabic often shows possession by attaching a pronoun directly to the noun.

Other examples:

• كتابي = my book
• بيتي = my house

Because in Arabic, adjectives usually come after the noun they describe.

So:

• القفل = the lock
• الرقمي = digital

Together:

• القفل الرقمي = the digital lock

This is the normal Arabic order:

• noun first
• adjective second

Unlike English, which says digital lock.

Because Arabic adjectives must agree with the noun in definiteness.

Here:

• القفل = the lock
• الرقمي = the digital

In good English we do not translate the second the, but in Arabic both words are definite.

So Arabic says, literally:

• the lock the-digital

That is simply how the digital lock is formed in Arabic.

If the noun were indefinite, the adjective would also be indefinite:

• قفل رقمي = a digital lock

No. It is not iḍāfa. It is a noun + adjective phrase.

Why not iḍāfa?

Because in iḍāfa:

• the first noun usually does not take الـ
• the second noun is another noun, not an adjective

For example:

• قفل الباب = the door’s lock / the lock of the door

But here:

• القفل is a noun
• الرقمي is an adjective describing the noun

So القفل الرقمي means the digital lock, not the lock of the digital thing.

Because ر is a sun letter.

When الـ comes before a sun letter, the l sound of الـ is not pronounced. Instead, the following consonant is doubled in pronunciation.

So:

• written: الرقمي
• pronounced: ar-raqamī

This happens in pronunciation, not in spelling.

Compare:

• القمر = al-qamar because ق is not a sun letter
• الرجل = ar-rajul because ر is a sun letter

Because Arabic has no separate indefinite article like English a/an.

So:

• مفتاح can mean a key or just key, depending on context
• المفتاح means the key

In this sentence:

• بدون مفتاح = without a key

The noun is indefinite, and Arabic does not need an extra word for a.

بدون means without.

So:

• بدون مفتاح = without a key

It functions like a preposition-like expression introducing what is absent.

In fully formal grammar, the noun after it is treated in the genitive:

• بدونِ مفتاحٍ

But in normal unvoweled Arabic writing, those case endings are usually not shown, so you just see:

• بدون مفتاح

A fully vocalized version could be written as:

• يَفْتَحُ صَدِيقِي القُفْلَ الرَّقْمِيَّ بِدُونِ مِفْتَاحٍ

These endings show the grammar:

• يَفْتَحُ: verb
• صَدِيقِي: subject
• القُفْلَ: direct object, so accusative
• الرَّقْمِيَّ: adjective matching القفل in case, definiteness, gender, and number
• بِدُونِ مِفْتَاحٍ: after a preposition-like expression, so مفتاح is genitive

In normal Arabic texts, these short vowels are usually omitted.

Yes.

The form يفتح does not force only one English translation. Depending on context, it can mean:

• opens
• is opening

So both are possible in English. Arabic often leaves that distinction to context, while English usually chooses one more specifically.

Yes. You could say:

• صديقي يفتح القفل الرقمي بدون مفتاح

This gives more prominence to صديقي.

So both are grammatical:

• يفتح صديقي القفل الرقمي بدون مفتاح
• صديقي يفتح القفل الرقمي بدون مفتاح

Very roughly:

• verb-first = more neutral/narrative in MSA
• subject-first = more emphasis on the subject or a more topic-comment feel