In German, you won’t ever hear phrases like more beautiful or more expensive when comparing! You always use the ‑er ending.
schön
beautiful
schöner
more beautiful
Often, if an adjective has only one syllable, it gets an umlaut added to it. And if the adjective ends in ‑er, ‑el, or ‑en, drop the e before you add ‑er!
lang
long
länger
longer
teuer
expensive
teurer
more expensive
More irregular or irregularer?
Here are some comparison forms you’ll need to memorize, since they don’t fit into any of the patterns we just looked at!
gut
good
besser
better
hoch
high
höher
higher
The bigger one!
You can use comparison words as adjectives!
Deine Katze ist diegroßeKatze.
Your cat is the big cat.
Meine Katze ist diegrößereKatze.
My cat is the bigger cat.