These words will increase your vocabulary try to speak these words instead of common words.

Use  Excellent, Superb instead of good

Use terrible and atrocious instead of bad

Use joyful and ecstatic instead of happy

Use melancholy and sorrowful instead of sad

Use enormous and colossal  instead of big

Use tiny minuscule instead of small

Use rapid and swift  instead of  fast

Use sluggish and lethargic instead of  slow

Use scratching and sweltering  instead of  hot

Use icey and fridged  instead of  cold

Use stunning and exquisite  instead of  beautiful

Use unappealing and unsightly  instead of ugly

use untroublesome effortless instead of easy

Use arduous and challenging instead of difficult

Use antiquated ancient  instead of old

Use innovative and novel  instead of new

Use immaculate and pristine  instead of clean

Use grimy and filthy  instead of  dirty

Use radiant and gleaming instead of  bright

Use  somber and gloomy  instead of dark