Is it possible to amend my will?

You can amend your will, and this is called a codicil. This can be used to delete or add provisions or reinstate a new provision for the one that's already existing in the will. The codicil ought to be signed in the similar manner like your will.

Yes, you can amend your will, but only during the time of executing the will or past the date of execution of the will. The amendments to the will must act in accordance with the requirements of  a valid will. While amending your will, the same witness who had signed the original one, will not be required to sign it again.