Android app development

I need an Android app. I would like it designed and built. I need an Android application related to education for 6-12 year old kids, when registering, users have to give the subjects they're interested in, from the subjects given in the list, his age and his location. once registered and logged in, they'll see activities and announcements related to those subjects. once they complete any of the activities (like watch videos, or any other activity), they receive xp. They also receive achievements, depending on the number of activities they complete. for example, if they complete 5 activities of science, they'll get the achievement of science pro or something like that. some of the activities require payment as well (like if a workshop is being held in the vicinity). The user has to buy coins (in app purchase) and spend that in order to book a seat for that activity. once they get 10 XP, they'll go to level 2 and the XP goes to 0. then when XP goes to 20, they go to level 2 and so on. they can ask questions and give answers to open questions. they need to spend coins to ask question. each question can get 5 answers max, then it'll be closed. once asked, the user can choose which answer is best and the user with best answer will get 60% coins spent by the user who asked the question. he can also choose worst answer. all the other answers, which are neither best not worst, will get the rest of the 40% of the coins equally distributed. the activities and recommendations are all shown depending on the tags user has selected, the location of the user and the age of the user. there are some small small features needed be added. I'll explain then in pm.