Schreiben, "Write" and "will write"
In English, "I write" and "I will write" are clear, but in German this does not seem to be so. "Ich Schreibe Morgen" translates as "I will write tomorrow". Why is the German not "Ich werde morgen schreiben".
In many languages the present tense is also used for the future.
I have an exam tomorrow
We're visiting my parents next week
Same applies for German.
Ich werde morgen schreiben is more correct and you would use this tense in written German, whereas Ich schreibe morgen is a bit informal and more common in spoken German.
In German, you could use present tense + a word for a future time ("morgen", "nächstes Jahr", "in 3 Wochen" etc.) when you want to talk about the future.
You only use future tense if you want to make a prediction (like: "morgen wird es regnen") or if you want to emphasize that something will happen in the future (e.g. "morgen werde ich Vokabeln lernen").
However, if there is no word for a future time in the sentence, then "Ich schreibe einen Brief" will always be understood as "I write a letter" (now) and never as something that will happen in the future.