המנהלת נתנה לי משוב כנה ואמרה שאני מדברת ברור ונשמעת בטוחה.

It is the Hebrew definite article, meaning the.

So:

• מנהלת = a female manager / manager
• המנהלת = the female manager / the manager

In this sentence, it refers to a specific manager already known from context.

Because the person doing those actions is female.

• מנהלת = female manager
• נתנה = she gave
• אמרה = she said

Hebrew verbs in the past tense agree with the subject’s gender and number, so since the manager is female, the verbs are feminine singular.

If the manager were male, you would get:

• המנהל נתן לי... ואמר...

לי means to me.

It is made from:

• ל־ = to
• י = me

So:

• נתנה לי משוב = gave me feedback

This is very common Hebrew word order with נתן:

• נתן לי = gave me
• נתנה לו = gave him
• נתנו לנו = gave us

Because את is used before a definite direct object, and משוב כנה here is indefinite.

So:

• נתנה לי משוב כנה = She gave me honest feedback
  no את, because it is honest feedback, not the honest feedback

Compare:

• נתנה לי את המשוב הכנה = She gave me the honest feedback

A good rule:

• use את before the...
• usually do not use את before a/an/some...

שאני is ש־ + אני and means that I.

So:

• אמרה שאני מדברת... = She said that I speak / am speaking...

After verbs like say, think, know, feel, Hebrew very often uses ש־ to introduce the next clause.

Examples:

• הוא אמר שאני צודקת = He said that I am right
• אני חושבת שהוא עייף = I think that he is tired

In everyday Hebrew, ש־ is the normal choice here.

Because the speaker, I, is female.

In Hebrew, present-tense forms agree with gender:

• אני מדברת = I speak / I am speaking said by a woman
• אני מדבר = I speak / I am speaking said by a man

So the sentence tells you that the person receiving the feedback is female.

Here ברור is being used in an adverb-like way, meaning clearly.

So:

• מדברת ברור = speaks clearly

Even though מדברת is feminine, the word ברור does not change here, because it is functioning more like an adverb than a normal adjective.

This is common in Hebrew:

• לדבר ברור = to speak clearly
• להסביר פשוט = to explain simply

You may also hear more formal alternatives in other contexts, but ברור here is very natural.

Literally, ונשמעת בטוחה is something like and is heard as confident, but in natural English it means and sounds confident.

Breakdown:

• ו־ = and
• נשמעת = sounds / is heard (feminine singular)
• בטוחה = confident (feminine singular)

So:

• מדברת ברור ונשמעת בטוחה = speak clearly and sound confident

This is a very natural way in Hebrew to talk about how someone comes across when speaking.

Because they also refer to אני, and the speaker is female.

In the clause:

• שאני מדברת ברור ונשמעת בטוחה

the subject is still I throughout. Since that I is feminine, the forms are feminine:

• מדברת
• נשמעת
• בטוחה

If a man were speaking, it would be:

• שאני מדבר ברור ונשמע בטוח

Because both parts share the same subject, so Hebrew does not need to repeat it.

The structure is:

• She said [that I speak clearly] and [sound confident].

Hebrew works the same way:

• שאני מדברת ברור ונשמעת בטוחה

The subject אני applies to both מדברת and נשמעת. Repeating it would usually be unnecessary unless you wanted extra emphasis.