I’ve lost some of my contacts for some reason?

First you need to determine how you are managing your contacts. Is it iCloud or another email service. Then what did you do before you lost these contacts. Open Contacts on the iPhone and check the upper left corner to see if All Groups is selected. You may have contacts in more than one group.

ajaz1966 wrote:

it all happened when I tried to change the email address in settings, no my email are also not coming through to mail app

Change what email address in Settings? You did not answer my question about how you were managing contacts, but given this statement, it would seem that you may have been managing them in this email account. Now that you have disrupted this account, you have lost access to your Contacts. I would start by trying to fix the connection of this account. I don't quite understand what you meant by "tried to change the email address in Settings", so it would help if you explained that.