Sajdah and Jalsah

Q: What are the dua's whilst in sajdah?

Q: If a person is incapable of making du’ā in Arabic during his salāh, may he make du’ā in any other language? I read that if he is able to make du’ā in Arabic, then there exists a difference of opinion in the permissibility of doing so in a different language while in salāh. According to Imām Abū Yūsuf and Imām Muhammad, it is impermissible and the prayer will not be valid.  On the other hand, according to Imām Abū Hanīfah, the prayer will be valid, but it is makrūh (disliked) to do so. Is this true? But the question is what if a person is incapable of making du’ā in Arabic during his salāh? Is it permissible without being makruh?

Q: If a person makes a sajdah on a warm hat which overlaps onto his forehead, will this be correct?