What should the person who is praying behind the imam do if the imamis silent for a long time after reciting al-Faatihah?

If the person who is praying behind the imam finishes reciting
al-Faatihah during a prayer in which Qur'aan is recited out loud, but
the imam does not start to recite after al-Faatihah, what shouldhe do
in this situation?.
Praise be to Allaah.
The answer to that is that we would say to theimam first of all: You
should not remain silent for this long time between reciting
al-Faatihah and reciting what comes after it. What is prescribed is
for the Imam to remain quiet briefly between al-Faatihah and the
soorah that comes after it so as to distinguish between the obligatory
recitation and the mustahabb recitation. During this silent pause it
is prescribed for the one who is praying behind the Imam to recite
al-Faatihah and complete the recitation, even if the imam recited it.
But as for the imam falling silent for a long time, this is contrary
to the Sunnah. Moreover, even if we assume that the imam did that and
remained silent for a long time, if the person praying behind him
recited al-Faatihah and completed it, he may recite a soorah after
thatuntil the imam begins to recite the soorah that comes after
al-Faatihah, at which point he shouldstop reciting, because it is not
permissible for theperson praying behind the imam to recite whenthe
imam is reciting, except with regard to reciting al-Faatihah only.End
quote.
Majmoo' Fataawa Ibn 'Uthaymeen (15/109)