Lot of problem with spidey suit

Guys I have the suit, but honestly I can not understand how you can sew.
And 'praticament impossible to get her well, the sleeves do not fit well, I entrusted the work to a dressmaker, however, is going crazy as well as the area behind the seats and under the genitals are absurd sewing.
I would be grateful if you could help me maybe with some pictures, maybe for those who have already 'sewn, can' be easy to advise me.
There is a good tutorial that explains well how the pieces are sewn?