i can not activate my ipad

Information and procedures for the Activation Lock:

https://support.apple.com/en-us/HT201365

If you are the original owner whose AppleID was last used to activate the device, you should be able recover a forgotten AppleID and associated password here:

https://iforgot.apple.com

More information about AppleID and password recovery is here:

https://support.apple.com/en-gb/HT201354

https://support.apple.com/en-gb/HT201487

Activation Lock is a theft deterrent. It’d be a very poor deterrent, if it were easy to bypass. You have here what is effectively a lost or stolen iPad. As stated in the reply above, you will need the Apple ID and password associated with the Activation Lock, or the original purchase receipt and matching photo ID and a discussion directly with the folks at Apple.

In addition to the above-reply links: The All Too Common SAD Reality of Buying a used iPad/iPhone - Apple Community