ふじさんは たかいです。/ Mt. Fuji is high.

AはBです。

use "A is B" grammer to explain about A with the adjective B.

ふじさんは　たかいです

ふじさん/Mt. Fuji. たかい/high. it means "Mt. Fuji is high.". I introduce common usuful adjectives with example sentences in the following.

さくらは　きれいです

"さくら / Cherry Blossoms", "きれい/beautiful". It means "The cherry blossoms are beautiful."