Ich freue mich über deine Nachricht, weil ich dich heute nicht sehen kann.

Because sich freuen is a reflexive verb in German. That means it normally uses a reflexive pronoun:

• ich freue mich
• du freust dich
• er/sie/es freut sich

In this sentence, mich does not mean me in the usual English sense. It is just part of the verb pattern sich freuen.

So:

• ich freue mich = I am happy / I’m glad
• not literally I make me happy

With sich freuen, German often uses two common patterns:

• sich freuen über + accusative = to be happy about something now or about something that has already happened
• sich freuen auf + accusative = to look forward to something in the future

So here:

• Ich freue mich über deine Nachricht = I’m happy about your message

If the message is already received, über is the natural choice.

Because über here takes the accusative case.

The phrase is:

• sich freuen über + accusative

Since Nachricht is feminine, the accusative form of deine is:

• nominative: deine Nachricht
• accusative: deine Nachricht

For this feminine noun, nominative and accusative look the same, so you do not see a change in the article.

A masculine noun would show the case more clearly:

• Ich freue mich über deinen Brief.

Dich is the accusative form of du.

The verb sehen usually takes a direct object, and the person being seen is that object:

• ich sehe dich = I see you

So in:

• weil ich dich heute nicht sehen kann

ich is the subject, and dich is the direct object.

Because weil introduces a subordinate clause, and subordinate clauses are separated by a comma in standard German.

So the sentence is divided into:

• main clause: Ich freue mich über deine Nachricht
• subordinate clause: weil ich dich heute nicht sehen kann

The comma is required in normal written German.

Because weil creates a subordinate clause, and in German subordinate clauses the conjugated verb goes to the end.

Compare:

• main clause: Ich kann dich heute nicht sehen.
• subordinate clause: ..., weil ich dich heute nicht sehen kann.

That final verb position is one of the most important word-order rules in German subordinate clauses.

This happens because können is a modal verb.

With modal verbs, German uses:

• a conjugated modal verb: kann
• plus an infinitive: sehen

In a subordinate clause, both go to the end, and the infinitive usually comes before the conjugated modal:

• ..., weil ich dich heute nicht sehen kann.

So the end of the clause is:

• sehen = infinitive
• kann = conjugated modal verb

Here nicht negates the idea of seeing you.

In German, nicht is often placed before the part it is most closely negating, or near the end of the clause if it negates the verbal idea more generally.

So:

• weil ich dich heute nicht sehen kann

means because I cannot see you today

The nicht comes before sehen kann as part of the verbal idea.

If you move nicht, the emphasis can change.

Heute is a time adverb. In German, time expressions often come before nicht when nicht is negating the verb phrase rather than the time word itself.

So:

• ich dich heute nicht sehen kann

sounds natural for I can’t see you today.

If you said:

• ich dich nicht heute sehen kann

that would sound unusual and would suggest a contrast like not today, but maybe another day.

So the word order in the original sentence is the normal, neutral one.

German capitalization has two important rules visible here:

1. The first word of a sentence is capitalized

   • Ich

2. All nouns are capitalized in German

   • Nachricht

That is why Nachricht has a capital letter even though English would write message with a lowercase letter.

Yes. Ich freue mich is grammatically present tense.

German often uses the present tense where English might use:

• I’m happy
• I’m glad
• I’m pleased

So although the German form is literally present tense, the natural English translation may vary depending on context.

It is grammatically possible, but it changes the emphasis and sounds less neutral.

• weil ich dich heute nicht sehen kann = the normal way to say because I can’t see you today
• weil ich dich nicht heute sehen kann = emphasizes not today specifically, as if contrasting today with another time

So the original sentence is the best standard version for most situations.