Contacts app runs slowly (beachballing) when adding contact or updating contact info. HELP!

probably a full iCloud account, or one larger than the free one trying to synchronize info, or a simultaneous backup tying up system resources. if none of them above, use Etrecheck to generate a full system report free and post to communities so we can find out what is ailing your machine. Do not use any system optimizers or third party software firewalls as these can slow down your machine if you don’t know what you are doing. Backup your data when not using your computer.