How to lock iPhone 15 Pro Max when someone has access to Apple ID?

If you have proof of purchase, the official Apple Support can disable the Activation Lock, so that you can set it up with your Apple Account again.

Have a look at this article:

Additional Support - Activation Lock

In case you have to get access to your Apple Account again:

If you think your Apple Account has been compromised - Apple Support

Note that if your ex-boyfriend has physical possession of the phone, and also has the phone registered with his Apple ID, one for which you do not know the password, there is no way to use Activation Lock to lock it.

Apple could perhaps remove his Apple ID (with sufficient proof of ownership), but you would then need physical possession of the phone to re-register it with your Apple ID. Physical possession that it does not sound like you have.

marija94 wrote:

my ex-boyfriend just take it as his phone and entered the apple id but a document that i am the owner?

The post by Servant of Cats about sums it up unless you go to the police and claim the iPhone has been stolen from you. Once you have possession of the phone again you could try using https://al-support.apple.com/#/additional-support to request Apple to unlock the iPhone. Apple will only do that if your "document" is the original receipt from when the device was purchased from Apple or an authorized retailer. If it is from another store then they likely will not accept it and it isn't worth the trouble of trying to recover the device.