אני מאמינה בו, כי הוא תמיד מנסה.

Because the speaker is female.

In Hebrew, the present-tense form often agrees with the subject’s gender and number. So:

• אני מאמינה = I believe (said by a woman)
• אני מאמין = I believe (said by a man)

So this sentence is being spoken by a woman. If a man said it, it would be:

• אני מאמין בו, כי הוא תמיד מנסה.

בו means in him here.

It is made from:

• ב־ = in
• a pronoun form meaning him

So:

• מאמינה בו = believe in him

This is a very common Hebrew structure. You usually do not say ב הוא in standard Hebrew for in him; instead, Hebrew uses the combined form בו.

Related forms:

• בה = in her
• בהם = in them (masculine/mixed)
• בהן = in them (feminine)

Because להאמין ב־ means to believe in someone or something.

This is an important distinction:

• להאמין ב... = to believe in / have faith in
  
  • אני מאמינה בו = I believe in him
• להאמין ל... = to believe someone
  
  • אני מאמינה לו = I believe him

So:

• אני מאמינה בו does not mean I believe what he says
• it means I have faith in him / I believe in his abilities or character

Here, כי means because.

It introduces the reason:

• אני מאמינה בו = I believe in him
• כי הוא תמיד מנסה = because he always tries

So the second part explains why the speaker believes in him.

A useful note: כי can also mean that in other sentences, depending on context.

In this sentence, הוא is very natural and usually expected.

One reason is that Hebrew present-tense verb forms do not show person as clearly as English-style conjugations do. מנסה tells you gender/number, but not by itself who the subject is supposed to be.

So:

• הוא תמיד מנסה = he always tries

Without הוא, the phrase could feel incomplete unless the context already made the subject totally clear.

מנסה is the present tense form of לנסות = to try.

Here it matches הוא, so it means:

• he tries
• he is trying (depending on context)

In this sentence, with תמיד, it clearly means he always tries.

Useful related forms:

• אני מנסה = I try / am trying
• הוא מנסה = he tries
• היא מנסה = she tries
• הם מנסים = they try
• הן מנסות = they try

Here it is masculine singular because the subject is הוא.

An interesting detail: in normal unpointed Hebrew spelling, the masculine and feminine singular forms of this verb are often written the same way:

• הוא מנסה
• היא מנסה

So the spelling does not change here, but the subject tells you whether it is he or she.

That is the most natural word order here.

• הוא תמיד מנסה = he always tries

In Hebrew, adverbs like תמיד (always) often come before the present-tense verb.

Other orders may be possible in some contexts, but הוא תמיד מנסה is the most neutral and natural choice.

Not exactly.

• אני מאמינה בו = I believe in him
• אני מאמינה לו = I believe him
• אני סומכת עליו = I trust him (said by a woman)

So believe in him and trust him are related ideas, but they are not the same phrase in Hebrew.

It comes from the root א-מ-נ, which is connected with ideas like belief, faith, and trust.

The dictionary form is:

• להאמין = to believe

From the same root, you may also see words like:

• אמונה = faith / belief
• נאמן = faithful / loyal

Seeing the root can help you recognize related vocabulary later.

Not always strictly required, but it is very normal.

Hebrew punctuation is somewhat flexible in short sentences. A comma before כי often marks a natural pause before the reason clause:

• אני מאמינה בו, כי הוא תמיד מנסה.

You may also see short sentences without the comma in informal writing, but with the comma is perfectly standard and clear.