I read in a Fatwa that the recitation of the al fatiha is invalidated if you make a too long pause while reading it. How long is that pause and is the ruling the same for other parts of Salah? When i feel that i mispronounced something i sometimes take a short break probably not more than 10 seconds to decide whether it's just waswas or an actual mistake, does that invalidat the recitation?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

This length that nullifies Al-Fatihah and prevents continuity [in reciting it] depends on the custom. The short pause like the aforementioned seconds, and even what is more than that, does not harm.

Moreover, a long interruption in other than Al-Fatihah and the Tashahhud does not harm, as stated by the jurists.

Ash-Sherbeeni said:

“Its issue – meaning the statement of An-Nawawi in al-Minhaaj – is that continuity is not a condition – i.e. in Tashahhud – but the most preponderant opinion is that it is an obligation as in at-Tatimah. Ibn ar-Rif’ah said: ‘It is by analogy to what has already been discussed about Al-Fatihah.” [End of quote]

You have to repel these whispers, not pay any attention to them, and not give in to them, for giving in to them will lead you to a great evil.

Allah knows best.