What should I do if I finish reciting Surat Al-Fatihah and a short surah in a silent congregational prayer, and the Imam has not yet said the Takbir (Allahu Akbar)? Should I remain silent or is it permissible for me to supplicate? And likewise, what should I do after finishing the Salatul Ibrahimiyyah (Ibrahimic prayer)?

It is permissible to recite more than one Surah (definition) in a single unit of prayer (rak'ah). Supplication after the Abrahamic prayer (Salat al-Ibrahimiyyah) is legislated, and among the authentic supplications are: "O Allah, I seek refuge in You from the punishment of the grave, and from the tribulation of the Dajjal (Antichrist), and from the trials of life and death, and from sin and debt." And, "O Allah, reckon with me an easy reckoning." And, "O Allah, I seek refuge in You from the evil of what I have done, and from the evil of what I have not done." And, "O Allah, I have wronged myself greatly, and no one forgives sins except You. So, grant me forgiveness from You, and have mercy on me, for You are the Forgiving, the Merciful." And, "O Allah, forgive me for what I have sent forth and what I have held back, and what I have concealed and what I have declared, and what I have exceeded in, and what You know better than me. You are the Advancer and You are the Delayer. There is no god but You." And, "O Allah, I seek refuge in You from stinginess and cowardice, and I seek refuge in You from being returned to the worst of old age, and I seek refuge in You from the trials of this world, and I seek refuge in You from the torment of the grave." And, "O Allah, I ask You, O Allah, by You being the One, the Unique, the Self-Sufficient, Who did not beget and was not begotten, and to Whom no one is equal, to forgive my sins, for You are the Forgiving, the Merciful." And, "O Allah, I ask You by my testifying that You are Allah, there is no god but You, the One, the Self-Sufficient, Who did not beget and was not begotten, and to Whom no one is equal." And, "O Allah, I ask You by the fact that to You belongs all praise, there is no god but You alone, without partner, the Bestower, O Originator of the heavens and the earth, O Possessor of majesty and honor, O Ever-Living, O Sustainer, I ask You for Paradise and I seek refuge in You from the Fire." And, "O Allah, by Your knowledge of the unseen and Your power over creation, keep me alive as long as You know life is better for me, and cause me to die when You know death is better for me. I ask You for Your fear in secret and in public, and I ask You for the word of sincerity in contentment and anger, and I ask You for moderation in poverty and richness, and I ask You for blessings that never end, and for comfort that never ceases, and I ask You for contentment after the decree, and I ask You for a cool life after death, and I ask You for the pleasure of gazing upon Your noble face, and the longing to meet You, without any harmful adversity or misleading trial. O Allah, adorn us with the adornment of faith, and make us guides who are guided."