With い adjectives, to conjugate the verb into positive, negative, present or past tense, you change the い to くない, かった or くなかった. But with な adjectives, you conjugate by changing です to ではありません, でした and ...
To say new, the first way that I learned is to use the i-adjective 新しい. But I noticed that the na-adjective 新たな is used a lot in written texts. Is there any difference in when either is used?
Japanese has two kinds of adjectives known by several terms but the ones I know are i-adjectives and na-adjectives - why? I recall that Japanese adjectives are much more like verbs than in English ...