Why do you give your coworker access to your Apple ID and other important things that you should not & never share?
Change your Apple ID password.
Create a strong password for your Apple ID, It is best if your password consists of eight or more characters and include upper and lowercase letters, and at least one number. You can also add extra characters and punctuation marks to make your password even stronger.
Never provide your password, passcode, security questions, verification codes, recovery key or any other account security details to anyone else. Apple will never ask you for this information.
Then see this Apple article: What to do after you change your Apple ID or password
What to do after you change your Apple ID or password - Apple Support
Check also. ⤵️
If you think your Apple ID has been compromised
If you think your Apple ID has been compromised - Apple Support
Manage and use your Apple ID
Manage and use your Apple ID – Apple Support (UK)
Get a verification code and sign in with two-factor authentication
Get a verification code and sign in with two-factor authentication - Apple Support
Check your Apple ID device list to see where you're signed in
Check your Apple ID device list to find where you're signed in - Apple Support
- if you see devices that don't belong to you, delete from your account.
how to remove my apple id from his family icloud by myself?
See this Apple article: Leave Family Sharing -> Leave Family Sharing - Apple Support
I hadn’t t buy 200 GB ICloud, but my icloud had upgraded to 5GB to 200gb. why my icloud storage has changed?
We don't know, ask your coworker.
Check -> Go to -> Settings -> your name -> iCloud -> if you see 50 GB (or 200 GB or 2 TB) then you have an iCloud subscription.
If you have an iCloud subscription, you will receive a monthly bill from Apple, check your email box.
You can downgrade again to 5 GB, see this Apple article: Downgrade or cancel your iCloud+ plan
Downgrade or cancel your iCloud+ plan - Apple Support (PH)