As with any language, there are certain rules when writting in German. This time we will go over the cases when the use of capital letters is necessary in the German language.
All nouns in German should be written with a capital letter.
Recht haben (to be right).
Heute Abend (this evening).
In the case of nouns, the use of capital letters is fairly easy: if it is a noun, it has to go in capital letters.
Pronouns are a bit trickier than nouns but not by a lot. Generally speaking the only German personal pronoun that must be capitalized is "Sie". And not even all the time. "Sie" written with capital S is only for when the word is used formally or as a courtesy pronoun. When it is used as "she, they, her or them" sie should not have a capital S (unless it is at the beginning of a sentence).
Ich sehe sie. ✔️ (I see her/them)
Was möchten Sie, Frau Smith? ✔️ (What would you like, Mrs. Smith?)
Out of habit, many German speakers still use capital letters in their emails or written letters. But it is not compulsory at all. Also, like many other languages, German does not use capital letters for the first-person singular pronoun ich (I) unless it is the first word in a sentence.