Adjectives

Hello,
Is there an easy way to quick memorize and study adjectives??
I think they are a little difficult to memorize.
For example.

atarashi: New
atatakai: warm
atsue: Hot
ooki: big
oishii: Delicious

These are what I have memorized so far....
The rest, when I try to memorize them I forget them after a bit of minutes....

It is good that you're forgetting them, because you have learned them incorrectly.

atarashii
atsui
ookii

Please do yourself a big favor by using a proper textbook and/or taking a class.