1. The Comparative

2. The Comparative of adjectives in English.
To form the comparative of an adjective, English adds -er to shorter words ("prettier") or places more in front of more complicated ones ("more beautiful").
Examples:
Adjective Comparative
nice nicer
Interesting more interesting
handsome more handsome

3. The Comparative of adjectives in German.
No matter how long the adjective or adverb, German always adds -er ("schöner", "interessanter"). Never use mehr for this purpose. Adjective endings follow the -er.
Examples:
Adjective Comparative
nett (nice) netter (nicer)
Interessant (interesting) interessanter (more interesting)
hübsch (handsome) hübscher (more handsome)

4. Some adjectives, almost always monosyllabic with an a, o or u, add an umlaut.
Adjective Comparative
arm (poor) ärmer (poorer)
klug (clever) klüger (cleverer)
scharf (sharp) schärfer (sharper)
jung (young) jünger (younger)
schwach (weak) schwächer (weaker)
kurz (short) kürzer (shorter)

5. Adjectives ending in -el or -er normally drop the -e- before the comparative -er:
Adjective Comparative
dunkel (dark) dunkler (darker)
teuer (expensive) teurer (more expensive)

6. Some adjectives change their stems in other ways, as well:
Adjective Comparative
gut (good) besser (better)
hoch (high) höher (higher)
viel (much) mehr (more)
bald (soon) eher (sooner)

7. als - than
If you are comparing two things in German, you will use als – than.
Examples
Die Maus ist kleiner als der Hund.
Das Pferd ist schneller als die Katze.
Biologie ist interessanter als Geschichte.
The mouse is smaller than the dog.
The horse is faster than the cat.
Biology is more interesting than History.