IslamQA: On praying (making dua) during salah and whether one can do it in English

What is the correct way to make dua during salah? For example if I wanted to make dua for someone or ask Allah for something how and when would i do that? I've been told saying it in English invalidates salah

There isn’t sufficient evidence from the Quran and the Sunnah to make a conclusive judgment about the issue of making dua in a non-Arabic language during salah.¹ It doesn’t seem to me that there would be any harm in it. This only applies to additional duas a person adds to the salah, the salah’s required parts should be conducted in Arabic.

As for when to make dua during salah, it can be done during prostrations (rukūʿ and sujūd) after saying the required words. For example, when you are making sujūd, say the required part (subḥāna rabbī al-aʿlā or any variant you have been taught) then make any dua you want before getting up. You can also do it when get up after the first sujūd and before the second one. You can also do it after getting up from rukūʿ and saying samiʿa llāhu li-man ḥamida but before going down to sujūd. Another time is before saying the salām at the very end of the prayer.