It is really essential that we recite certain parts of our prayer in the Arabic language, but this has to do mainly with the revealed words of Allah Ta’ala from the Qur’an. These words by themselves are inimitable and unsurpassed in their meaning and style since they are the exact words of Allah Ta’ala. So, we are required to say these words in the original language. Besides that, personal supplication can be made in one’s own language.