Do not read every verb as فَعَلَ. The middle vowel is part of the learned verb: عَلِمَ and كَرُمَ are different patterns.
Do not guess from translation alone. Knowing that a verb means ‘he heard’ does not by itself supply the Arabic middle vowel; learn سَمِعَ as a complete form.
Do not confuse the ending with the lexical pattern. In شَرِبْنَا, ـْنَا means ‘we,’ while the basic verb remains شَرِبَ on فَعِلَ.