Until now my son have used my phone (iphone) and my google account to play Pokomon go. But now he got his own phone (an andoid) and his own google account. But when he open Pokemon go he is automatically looged in with his own gmail/google account and thus starts from scratch. It it possible to transfer my prograssion to his new account? Or to chainge the email used to the account?
You cannot transfer progress from one account to another, but you can allow him to use yours. To do this, add your Google account to his phone (should be an option in the phone's system settings). Once there are multiple Google accounts on the phone, then Pokemon Go should prompt for which one you want to use. If it doesn't, go into the permission settings for the app (again, this should be an option in the system settings somewhere) and remove the contacts permission.
Unfortunately I can't give specific instructions for how to change the settings, as it depends on the specific phone and OS version.
Obviously if you do this, your Google account will be on his phone, and he may be able to use it for other things. It's up to you whether or not you're okay with that, but it's your only option for letting him keep his progress.