Common mistakes
The second and third radicals are the same letter. They merge: رَدَّ: and come apart again before a consonant ending: رَدَدْتُ.
قَلَلَ → قَلَّ Past: heقَلَلَتْ → قَلَّتْ Past: sheقَلَلُوا → قَلُّوا Past: they (m.)يَقْلِلُ → يَقِلُّ Present: he