मैं तुमसे सहमत हूँ।

A word-by-word breakdown is:

• मैं = I
• तुमसे = with you / from you
  Here it means with you in the sense of agreement.
• सहमत = in agreement / agreed
• हूँ = am

So the structure is basically:

• I + with you + in agreement + am

That is why the full sentence means I agree with you.

Hindi often uses a postposition where English uses a preposition.

Here, से is the postposition attached to तुम:

• तुम = you
• तुमसे = with you / from you / than you, depending on context

With सहमत, Hindi normally uses से to express agreement with someone:

• मैं तुमसे सहमत हूँ। = I agree with you.
• मैं उससे सहमत हूँ। = I agree with him/her.

So तुम alone would not sound correct here. The verb/adjective सहमत requires से for the person you agree with.

Not exactly. सहमत is usually treated as an adjective meaning agreeing or in agreement.

So the sentence is literally more like:

• I am in agreement with you

That is why हूँ is needed:

• सहमत = in agreement
• हूँ = am

Together:

• सहमत हूँ = am in agreement

This is a very common pattern in Hindi: an adjective or predicate word + a form of होना (to be).

हूँ is the first-person singular present tense form of होना (to be).

Because the subject is मैं (I), you use हूँ:

• मैं ... हूँ = I am ...

Compare:

• मैं सहमत हूँ। = I agree.
• तुम सहमत हो। = You agree.
• वह सहमत है। = He/She agrees.
• हम सहमत हैं। = We agree.

So हूँ matches मैं.

Usually, सहमत stays the same for both masculine and feminine speakers in normal modern Hindi.

So both a man and a woman can say:

• मैं तुमसे सहमत हूँ।

Unlike some adjectives, सहमत does not usually change to mark gender in everyday usage.

तुम is informal to neutral, depending on the relationship and region.

Hindi has different levels of you:

• तू = very intimate / very informal / sometimes rude
• तुम = casual, familiar, normal with friends, siblings, some peers
• आप = polite, respectful, formal

So:

• मैं तुमसे सहमत हूँ। = I agree with you.
  (casual/familiar)
• मैं आपसे सहमत हूँ। = I agree with you.
  (polite/formal)

A learner should be careful: when in doubt, आप is safer.

Use आपसे instead of तुमसे:

• मैं आपसे सहमत हूँ।

This is the polite/respectful version of I agree with you.

You can think of the pattern as:

• मैं + [person] + से + सहमत हूँ

Examples:

• मैं उनसे सहमत हूँ। = I agree with them / him / her (respectful)
• मैं राम से सहमत हूँ। = I agree with Ram

Yes, often you can, if the context already makes the subject clear.

So both of these work:

• मैं तुमसे सहमत हूँ।
• तुमसे सहमत हूँ।

Hindi often leaves out subjects when they are understood from context.
But for learners, keeping मैं can make the sentence easier to understand and produce correctly.

The natural Hindi order is:

• मैं (subject)
• तुमसे (object/complement with postposition)
• सहमत (predicate adjective)
• हूँ (copula)

So the pattern is roughly:

• Subject + with-person + in agreement + am

Hindi usually puts the verb or copula near the end, unlike English.

That is why हूँ comes at the end, not after मैं.

Yes. That means something like:

• I agree with what you said
• I agree with your point
• I agree with your statement

Breakdown:

• तुम्हारी बात = your statement / your point / what you said
• से = with
• सहमत हूँ = am in agreement

So there is a small difference:

• मैं तुमसे सहमत हूँ। = I agree with you
• मैं तुम्हारी बात से सहमत हूँ। = I agree with your point / what you said

Both are common.

A simple learner-friendly pronunciation is:

• main tum-se sah-mat hoon

A few notes:

• मैं sounds roughly like main but nasalized
• से sounds like say
• सहमत is sah-mat
• हूँ is hoon, with nasalization

If you want a more careful feel:

• मैं = nasalized maĩ
• हूँ = nasalized hū̃

You do not need perfect nasalization at first to be understood, but it is good to notice it.

Yes, मैं तुमसे सहमत हूँ is a very standard and natural way to say it.

Other possible expressions exist, for example:

• मैं तुम्हारी बात मानता हूँ = I accept your point / I believe what you say
• मैं भी ऐसा ही सोचता हूँ = I think so too

But for a direct translation of I agree with you, मैं तुमसे सहमत हूँ is one of the clearest and most common choices.

You keep सहमत and change the form of होना:

• मैं तुमसे सहमत था। = I agreed / I was in agreement with you.
  (masculine speaker)
• मैं तुमसे सहमत थी। = I agreed / I was in agreement with you.
  (feminine speaker)
• मैं tumसे सहमत रहूँगा। = I will remain in agreement with you.
  (masculine)
• मैं तुमसे सहमत रहूँगी। = I will remain in agreement with you.
  (feminine)

In the present tense, हूँ does not show gender, but in the past and future, gender often becomes visible.