Is It Permissible to Make Du`a in Other than Arabic?
Question

i was searching for fatwas on making dua in sujood of the fard salah in english or other languages and i got different fatwas from the site 11588  and 20953 
Please clarify this issue. Secondly my question is , i understand that you can make dua in english given you don't know arabic, but what i really am asking is that even one knows arabic can one FORMULATE his own Duas be it in arabic or any other language by using his own words and not saying dua that the prophet (pbuh) used to make or dua that are reported of him making. and 3) if that's the case shouldn't one be able to make dua in any language even though he knows arabic because ALLAH without a doubt understands all languages.
Praise be to Allah.Offering Du`a in other than Arabic in prayer 
Offering supplication (Du`a) in a language other than Arabic in the prayer is a matter concerning which there is a difference of opinion among the jurists. Some of them regard it as prohibited, some regard it as disliked and some regard it as permissible for the one who is not able to speak Arabic.
What is mentioned on our website is not contradictory. We followed the view that it is permissible to offer supplication in a language other than Arabic for one who is not able to speak Arabic, in our answer to question no. 20953 .
With regard to question no. 11588 , it quoted the fatwa of Shaykh `Abd Al-Karim Al-Khudayr (may Allah preserve him). Our approach when quoting fatwas of the scholars is to quote the fatwa as is, even if it differs from the view favoured by this website.
There follow the views of the jurists concerning this matter:
It says in Al-Mawsu`ah Al-Fiqhiyyah (11/172):
“Offering supplication in a language other than Arabic in the prayer:
What is narrated from the Hanafis regarding supplication in a language other than Arabic is that it is disliked, because `Umar (may Allah be pleased with him) forbade speaking non-Arabic languages. The apparent reason for that is that offering supplication in a language other than Arabic is contrary to what is preferred, and that when it is described as disliked, it is in the sense of it being not what is preferred.
It is not far-fetched to say that offering supplication in foreign languages is disliked in the sense that it is almost prohibited in the case of the prayer, and in the sense of it being not what is preferred outside of prayer.
The Malikis are of the view that it is prohibited to offer supplication in a language other than Arabic – according to what Ibn `Abidin narrated from Al-Qarrafi – because it is contrary to the veneration that is due to Allah. Al-Laqqani interpreted the words of Al-Qarrafi as referring to supplication in foreign languages the meaning of which is not clear, based on what he gave as the reason, which is that using a foreign language is contrary to showing respect and veneration to the Lord.
But if the meaning (of the supplication in the foreign language) is known, then it is permissible to use it in all cases, in the prayer and otherwise, because Allah, may He be exalted, says (interpretation of the meaning): {And He taught Adam the names} [Al-Baqarah 2:31] and {And We did not send any messenger except [speaking] in the language of his people} [Ibrahim 14:4]. This was also clearly stated by Ad-Dusuqi.
The Shafi`is discussed the matter in detail and said: The supplications that are offered in the prayer are either narrated in reports or are not narrated.
Offering supplications narrated in reports in a language other than Arabic
With regard to the supplications that are narrated in reports, there are three views concerning them:

The soundest view, which is the same as the view of the Hanbalis, is that it is permissible to say them in a language other than Arabic for one who is unable to speak Arabic, but that is not permissible for one who is able to speak Arabic, and if he does that then his prayer is rendered invalid.
The second view is that it is permissible for one who is able to speak Arabic and others.
The third view is that it is not permissible for either, because there is no need for that.

Offering supplications not narrated in reports in a language other than Arabic
With regard to supplications in the prayer that were not narrated in reports, it is not permissible to invent supplications in foreign languages, according to unanimous scholarly opinion.
As for other Adhkar – such as the first Tashahhud, sending blessings on the Prophet (blessings and peace of Allah be upon him), Qunut , Tasbih when bowing and prostrating, and Takbir when moving from one posture of the prayer to another – then according to the view that it is permissible to recite supplications in foreign languages, it is more apt that it be permissible in these cases. Otherwise, as to the question of whether that is permissible for one who is unable to speak Arabic, there are several views.
The soundest view is that it is permissible. The second view is that it is not permissible, and the third view is that it is permissible with regard to the parts of the prayer which, if omitted, can be compensated for by doing the prostration of forgetfulness (Sujud As-Sahw).”
Offering supplications that were not narrated in reports when one is unable to speak Arabic
It is permissible for a person to offer supplications that were not narrated in reports, even if that is in colloquial Arabic or in a language other than Arabic, outside of the prayer, or in the prayer when one is unable to speak Arabic, provided that he use any permissible words and avoid transgressing the limits, and provided that his supplication does not involve any sin or severing of ties of kinship.
Undoubtedly there is much good in the supplications that are narrated in reports, but a person may need to offer supplication for himself or for a loved one for some of the good things of this world and the hereafter, or he may need to ask Allah to ward off some harm or evil from him. This kind of supplication is broad in scope, and he does not have to limit himself to what is narrated in reports.
What is important in supplication is focus and presence of mind, and sincerity in turning to Allah, may He be exalted, no matter what language one is speaking. Allah, may He be exalted, hears all voices and understands all languages, and not even an atom is hidden from Him on earth or in the heavens.
Shaykh Al-Islam Ibn Taymiyah (may Allah have mercy on him) said: 
“As for the one who calls upon Allah with sincere devotion, offering a permissible supplication, Allah hears him and answers his supplication, whether his supplication is offered in flawless classical Arabic or otherwise.
In fact, if the one who offers supplication does not usually speak in flawless classical Arabic, then he should not try to put extra effort into doing so. Some of the early generations noted that if he focuses on trying to speak in flawless Arabic, he will lose his focus.
It is also disliked to try too hard to make one’s supplication rhyme, but if that happens without putting in extra effort, there is nothing wrong with it.
Supplication should stem from the heart and only express what is in the heart. The one who tries too hard to make his supplication in flawless classical Arabic will find that that undermines his presence of mind.
The one who is in desperate need calls upon Allah from his heart, in whatever phrases Allah enables him to say, spontaneously. This is something that every believer experiences in his heart. It is permissible to offer supplication in Arabic and in languages other than Arabic.
Allah, may He be glorified, knows what the one who is offering supplication is seeking, even if he does not speak grammatically, for He knows each of the clamour of voices, in different languages, and He knows their various needs.” (Al-Fatawa Al-Kubra 2/424)
Another indication that it is permissible to offer supplications in the prayer that were not narrated in reports is the words of the Prophet (blessings and peace of Allah be upon him): “Then let him choose whatever supplications he wishes.” (Narrated by Al-Bukhari (835) and Muslim (402) This is referring to supplication before the Taslim in the prayer.
Shaykh Ibn Baz (may Allah have mercy on him) said: 
“There are many hadiths that speak of this matter, which indicates that it is prescribed at these points in the prayer for the Muslim to offer whatever supplication he likes, whether that has to do with the hereafter or with his worldly interests, on condition that his supplication does not involve any element of sin or severing of ties of kinship. The best is to recite a lot of the supplications that were narrated in reports from the Prophet (blessings and peace of Allah be upon him).” (Fatawa Ash-Shaykh Ibn Baz, 11/172)
In conclusion, it is permissible to offer supplications in a language other than Arabic in the prayer, for one whose language that is, especially if it is difficult for him to learn Arabic. He may offer supplication and ask for whatever he wishes of goodness in this world and the hereafter, and it is not stipulated that it should have been narrated in reports.
And Allah knows best.