Why 'wengi' with 'w-' here (as if from Class 2)? My dictionary says that 'tembo' is a class 9/10 noun, so I would expect 'tembo nyingi' here.
Animate objects in the N/N class get M/Wa concords, with the exception of the possesive pronouns, e.g. dada zangu: my sisters, but nina dada wengi: I have many sisters.
why ina and not kuna?
That would mean 'There are many elephants in Manyara park'.