Du'aa are the most powerful weapon for a believer. Does these Du'aa have to be in Arabic or English? We can make Du'aa for almost anything, right? How many Du'aa are in the Qur'aan?
Thank you and take care. May Allah bless you and your family in this life and the Hereafter.

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.

No doubt, supplicating to Allaah is among the strongest weapons of a Muslim as the questioning sister has mentioned. The Prophet said: "Supplicating Allaah is the core of worship," then the Prophet recited the verse: {And your Lord says, Call upon Me; I will respond to you.” Indeed, those who disdain My worship will enter Hell [rendered] contemptible.}[40:60]."

As for whether the supplication should be in English or Arabic, if one can supplicate in Arabic knowing the meaning of what he supplicates then it is better. If one is not able to make supplications in Arabic then he may supplicate in a language he knows. It is preferable to include in his supplications the translations of the supplications found in the Qur'aan and sound Sunnah since they consist of the goodness of this life and the Hereafter.

As regards the question 'can we supplicate for almost anything' the answer is 'yes'! A Muslim can ask Allaah for the goodness of this life and Hereafter as well. It is not allowed to supplicate for something forbidden or to sever ties of kinship. The Prophet said: "Allaah will respond to the supplication of a person or protects him from misfortune equal to his supplication as long as it does not contain sin or severing ties with kinfolks." [At-Tirmithi]

The Prophet also said: "One's supplications are responded to as long as   he does not ask for a forbidden thing, or severing ties with kinfolk or hasten and say "I supplicated but it was not accepted and then gives up making supplication." [Al-Adab al Mufrad]

A Muslim should not limit his supplications to only worldly matters and forget the Hereafter. Allaah says (interpretation of meaning): {…And among the people is he who says, ‘Our Lord, give us in this world,’ and he will have in the Hereafter no share.}[2:200].

Imaam Al-Qurtubi said: 'The threat in the verse may even include a believer as well if his supplications are limited only to the worldly matters.'

We can not mention all the Qur'aanic supplications however, some of them are as follows:

1)     {‘Our Lord, give us in this world [that which is] good and in the Hereafter [that which is] good and protect us from the punishment of the Fire.’}[2:201].

2)     {“Our Lord, do not impose blame upon us if have forgotten or erred.}[2:286].

3)     {[Who say], “Our Lord, let not our hearts deviate after You have guided us and grant us from Yourself mercy. Indeed, You are the Bestower.}[3:8].

4)     {“Our Lord, indeed we have believed, so forgive us our sins and protect us from the punishment of the Fire.”}[3:16].

5)     {…“Our Lord, forgive us and our brothers who preceded us in faith..}[59:10].

Allaah knows best.