Prayers Must be in Arabic
All Scholars agree that anyone who offers his prayers must read the al-fatiha and the Quran in Arabic. it is not possible to use translation , if a person does not know the Fatiha ,but knows another passage of the Quran , he is required to say in each rak’ah a passage of similar length to the Fatiha. if he dows not know any part of the Quran in Arabic , he must learn . if he fears that he would miss his prayers before he could learn , he should glorify ALLAH , using the well known formula: subhan ALLAH, ALhamdulillah, La ilaha illa ALLLH, Allahu Akbar, La hawla wala qowwata illla billah. if a person con not learn all these five phrases, he learns what he can of them and repeats them.
this is the case of a man who could not learn any verse of the Quran : the Prophet (sallahu alihi wa sallam)taught him a few simple phrases in Arabic to repeat them in his prayers, he did not tell him to glorify ALLAH in silence.
therefor, when you offer your prayer , you should say the Quran in Arabic and also any glorification or supplication. when you have finished your prayers , you can say any supplication in your language. supplication in prayer can concentrate on what you have learned to say in Arabic. if you learn one sentence, to appeal to ALLAH to admit you into heaven and spare you any punishment in the hereafter, that is more than sufficient. you can include everything else in your supplication after prayer in your language.
it is not true that the Prophet and his companions used Arabic because it was their mother tongue, The Prophet (sallahu alihi wa sallam) used Arabic in prayer because he had to read the Quran in prayer and the Quran ALLAH’s words, is in Arabic. any translation of it is not the Quran ,but an explanation of its meaning. that translator may have to change the order of the original text on order to fit his text with the grammar into which he is translating. No one can change the order of the Quranic words. Had ALLAH wanted the Prophet (sallahu alihi wa sallam) to offer his prayers in any other language, he would have told him so and would have made it easy for him to learn that language. but ALLAH wants us to use his BOOK in our prayer , As it is well known to everyone , His Book has been revealed in Arabic.
if someone is praying with gathering , must remain silent. recitation of Imam is enough for him