in my pry i think that i should say at the end of tachahhod"oua achhadou anna mohamad rassoulou allah" but i found that it isn t true and i should say "oua achhadou anna mohammed abdohou oua rassoulouh" my question is my pry true?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

The phrase which you used to say before and the one which you learnt recently are both authentic.

The phrase which you learnt recently is confirmed by the narration of Ibn Mas'ood which reads: "Ash-hadu Allaa Ilaaha Illallaah Wa Ash-hadu Anna Muhammadan 'Abduhu Wa Rasooluh." (I bear witness that none has the right of being worshipped but Allaah and I bear witness that Muhammad is His Slave and Messenger.) [Al-Bukhari and Muslim]  And what you used to say before is narrated by Ibn 'Abbaas that the Prophet said: "Ash-hadu Allaa Ilaaha Illallaah Wa Ash-hadu Anna Muhammadan Rasoolullaah." (I bear witness that none has the right of being worshipped but Allaah and I bear witness that Muhammad is the Messenger of Allaah.) [Muslim]

Allaah Knows best.