One of the first lines is creating variables. Ignoring most of it, we’re focusing on the parts where GetSpellInfo = GetSpellInfo. Needs to be GetSpellInfo = C_Spell.GetSpellInfo.
local C_NamePlate_GetNamePlateForUnit, C_NamePlate_GetNamePlates, CreateFrame, UnitDebuff, UnitBuff, UnitName, UnitIsUnit, UnitIsPlayer, UnitPlayerControlled, UnitIsEnemy, UnitIsFriend, GetSpellInfo, table_sort, strmatch, format, wipe, pairs, GetTime, math_floor =
C_NamePlate.GetNamePlateForUnit, C_NamePlate.GetNamePlates, CreateFrame, UnitDebuff, UnitBuff, UnitName, UnitIsUnit, UnitIsPlayer, UnitPlayerControlled, UnitIsEnemy, UnitIsFriend, C_Spell.GetSpellInfo, table.sort, strmatch, format, wipe, pairs, GetTime, math.floor