Manahil is a non-Quranic Arabic name for girls that means "fountain", "spring". It is pronounced as (MU)st + (NA)p + (HI)m + p(L)ay, with the stress on the second syllable (the na part). It is spelled as مناهل in Arabic and can be spelled as Manaahil, Manahel, Manaahel, Menahil, Menahill, Manaahil in English.
Since the meaning of Manahil is good, it is an acceptable name for Muslims.
Some Pakistani websites is telling wrong meaning of Manahil as Door to Heaven. The accurate meaning is fountain (فوارہ) and spring (موسم بہار).