أحتاج إلى ثقتك.

• أحتاج = I need / I am in need of
• إلى = a preposition, here meaning something like to
• ثقتك = your trust

So the structure is:

verb + preposition + noun with a possessive suffix

A more fully vowelled version would be:

أحتاجُ إلى ثِقَتِكَ
or, if speaking to a woman, أحتاجُ إلى ثِقَتِكِ

Because in Modern Standard Arabic, the verb احتاج normally takes إلى before the thing needed:

• أحتاج إلى وقت = I need time
• نحتاج إلى مساعدة = We need help

So احتاج إلى is the standard pattern in MSA. Even though English uses a direct object, Arabic usually uses this preposition here.

أحتاج is the 1st person singular imperfect form of the verb احتاج.

That means:

• أحتاج = I need
• تحتاج = you need / she needs
• يحتاج = he needs
• نحتاج = we need

The initial أ here is the normal imperfect marker for I.

Because Arabic verbs already show the subject.

So أحتاج already means I need, and you do not have to add أنا.

You can say:

• أحتاج إلى ثقتك = neutral
• أنا أحتاج إلى ثقتك = more explicit or emphatic

Both are correct, but the version without أنا is very normal.

ثقتك is made of:

• ثقة = trust
• ـك = your

So literally it is trust-your, which Arabic uses to mean your trust.

There is no الـ because a noun with an attached possessive pronoun is already definite. In other words, ثقتك already means your specific trust, so الـ is not needed and would be wrong here.

Because ثقة ends in ة (taa marbuuTa). When a suffix is attached, that ة is pronounced as t.

So:

• ثقة on its own: often pronounced roughly thiqah in pause
• ثقتك: pronounced thiqatuka / thiqatika depending on case and context

This is very common in Arabic:

• سيارة = car
• سيارتك = your car

After the preposition إلى, the noun is in the genitive case.

So the fully vowelled form is:

• to a man: أحتاجُ إلى ثِقَتِكَ
• to a woman: أحتاجُ إلى ثِقَتِكِ

The important thing to notice is the i sound before the suffix, because prepositions in Arabic normally make the following noun genitive.

If speaking to one man:

أحتاجُ إلى ثِقَتِكَ
aḥtāju ilā thiqatika

If speaking to one woman:

أحتاجُ إلى ثِقَتِكِ
aḥtāju ilā thiqatiki

A few pronunciation notes:

• ح is a strong breathy h
• ث sounds like th in think
• إلى is ilā, with a long ā

Not by itself in normal unvowelled writing.

ثقتك can mean:

• your trust addressed to a man: ثِقَتِكَ
• your trust addressed to a woman: ثِقَتِكِ

In everyday Arabic writing, short vowels are usually omitted, so the same spelling can represent both. You know which one is meant from context.

Yes, أحتاج إلى ثقتك is a natural and correct MSA sentence.

Another common MSA wording is:

أنا بحاجة إلى ثقتك
literally, I am in need of your trust

That version is also very natural, especially in formal writing or speeches. But أحتاج إلى ثقتك is perfectly standard and direct.