since intrepreation can be taken in many ways, translations can vary. this is why i wrote 2 variations. #1 is directly translated from question’s quoting sentence. #2 is a little different; it means “little not / not very good at speaking japanese”.

(1) （私は）日本語がちょっと良くないです。
watashi ha nihongo ga chotto yokunai desu.

OR

(2) 日本語で話して（ちょっと）良くありません。
nihongo de hanashite (chotto) yoku arimasen.

watashi — i / me / self

ha — topic particle (reads as “wa” when in particle function)

nihongo — japanese language

ga — subject particle

de — particle of method — location / means of action, cause of effect.

chotto — a little、short time, just a minute.

yokunai — negative conjugation of ii/yoi which means good.

hanashite — te-form of hanasu — to speak.

yoku arimasen — polite version of yokunai, -masu form/conjugation.

desu — is / to be

sometimes, depending on how you want to say it, you can replace the ちょっと with 余り (amari) which is a “very” used for negatives. the positive and regular use one is とても (totemo)