I know a person who does not believe that there is god. He asked me if God is All-Knowing and able to do all things can God make himself dead and change your destiny if He want? If He changes there is no Qadar. Please answer me that I can convince him and prove that he is wrong.

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Allah, The Exalted, is Able to do all things that are possible and imaginable (it is not possible nor imaginable to be present and absent in the same place and at the same time).
As for what is impossible nor imaginable such as 'if Allah can make Himself dead or create another match to Him', He wills not such things and they are impossible to be since they are unimaginable and unconceivable by a sound mind.
Sheikh al-Islam Ibn Taymiyah (may Allah's mercy be upon him) said: 'According to Ahl al-Sunnah, Allah is Able to do all things; such things that are possible are included in this concept. As for what is impossible in itself like if something is existing and non-existing at the same place and in the same time, such a thing is in fact false and unimaginable. There is no difference among sensible people concerning the above-mentioned. So, the issue of 'if Allah can create another match to Him and so on' is included in the above ruling' .
As for al-Qadar (Divine Destiny), Allah has created people and has decreed their life, livelihood, words, deeds, etc. before creating them; He knows everything and all decrees are written in al-Lauh al-Mahfooz even things that Allah has decreed to be abrogated or changed. Every thing has been decreed by Him.
For more detail, on al-Qadar, check our Fatwa: 81893.
Allah knows best.