There are three patterns of declension for adjectives depending on whether they are accompanied by a definite article, indefinite article or no article.

Declension of adjectives preceded by a definite article
This chart shows you how an adjective's form changes when there is a definite article. The pattern has only the endings -e and -en.

Example:
Wollen Sie die graue oder die schwarze Tastatur?

Declension of adjectives preceded by an indefinite article
The declension following an indefinite article also applies to the possessive determiners (possessive adjectives) "mein", "dein", "ihr", etc. and the negation article "kein". In the singular in the nominative and accusative cases, the adjective changes to reflect the endings of definite articles. Since the indefinite article has no plural, the adjective endings are shown here using the example of "kein".

Example:
Hier ist Ihr neuer Arbeitsplatz.

Declension of articles when there is no article
This pattern is common for the plural, but rare in the singular. You need it, for instance, after ordinal numbers "two" and up.
In the nominative and accusatives cases, the adjective changes to reflect the endings of definite articles.

Example:
Jeden Tag gibt es drei warme Gerichte.