It is proved that every Menger quasigroup (grouplike Menger algebra) is an ft-algebra, Relations between such algebraic notions as homomorphism, subquasigroup, congruence relations and so on of a Monger quasigroup and the corresponding notions of its decomposition algebra are found. A criterion for the group isotope to be a superassociative is established Some main algebraic notions in superassociative group isotopes are considered