most of my contacts are missing after i connect my phone to my car's andorid multimedia.

Hi medemir,

Welcome to Apple Support Communities.The contacts on your iPhone shouldn't be impacted by a connection such as CarPlay. Has anything else recently changed such as removing an email account? Your contacts are associated with your email accounts or iCloud. Try the below steps from Manage and delete contacts on your iPhone, iPad, or iPod touch - Apple Support to make sure that contacts are enabled for all accounts.

"Turn Contacts on or off for an account

Want to add or remove all of the contacts from an account that you already set up? Just turn Contacts on or off for that account:

1. Go to Settings > Contacts > Accounts.
2. Tap the account that has contacts that you want to add or remove.
3. To add contacts, turn on Contacts. To remove contacts, turn off Contacts, then tap Delete from My iPhone."

Take care.