Okay, I will help you with filling in the adjective endings in the sentences.

Задание 1

Lachen ist die beste Medizin.

Explanation: Here, "die beste" is the nominative feminine singular form of the adjective "gut" in its superlative form.

Задание 2

Die dicken Bücher meiner Oma.

Explanation: Here, "die dicken" is the nominative plural form of the adjective "dick".

Задание 3

Die kleine Berührung tut gut.

Explanation: Here, "die kleine" is the nominative feminine singular form of the adjective "klein".

Задание 4

Gibst du mir den roten Füller?

Explanation: Here, "den roten" is the accusative masculine singular form of the adjective "rot".

Задание 5

Danke für das leckere Essen.

Explanation: Here, "das leckere" is the nominative neuter singular form of the adjective "lecker".

Задание 6

Peter hat die richtige Antwort gegeben.

Explanation: Here, "die richtige" is the accusative feminine singular form of the adjective "richtig".

Задание 7

Ich schicke einen langen Brief.

Explanation: Here, "einen langen" is the accusative masculine singular form of the adjective "lang".