I forgot my iCloud ID and password on my iPhone 13 Pro Max

If you are talking about "activation lock" (an anti-theft measure), AND if you cannot remember or don't know the old Apple ID & Password (even using these instructions:--> If you forgot your Apple ID email address or phone number - Apple Support or these:--> If you forgot your Apple ID password - Apple Support ) neither we, just users like you, nor Apple can help you, sorry, unless you are the original owner and you still have the proof of purchase (receipt/invoice reporting your device’s IMEI or Serial Number). Should be this case, start your request using this link: https://al-support.apple.com/#/additional-support

Shouldn’t be this case, activation lock can be removed only by the previous owner, with the credentials that were used to activate that iPhone/iPad. Without those credentials, that device is useless to you.

You can also take a look at this support article:--> How to removeActivation Lock- Apple Support

Regards

Giulio

The related article link at the top of this page is the right article which tells you what you need to do. What happened when you did as it suggests?

Typically your Apple ID is your email address and the same email you used to sign into this forum. Then to fix the forgotten Apple ID Password, you click the blue link in the article which is this --> https://iforgot.apple.com/password/verify/appleid