Language teaching app and pc

I am looking for someone who has knowledge in building online language teaching tool and/or apps. I have my own method of teaching English online and I would like to develop custom practicing apps / tools for my students. This consists of word games (memory cards, falling words, matching words, etc.) as well as practicing sentence building from very basic sentences to more complicated, with type of practicals like (translating a sentence from native to english and vice versa, writing down a sentence by hearing it, changing the type of sentence, ie. change it from question to negation, or from statement to question, etc., building sentences from words). I also want the program to check the answer and if faulty, give the correct answer. I would like a system developed where I can add and remove sentences, like in Quizlet and I can build practicals based on what level the students are. I would like to know a ballpark figure of what would this cost or if anyone know a similar system that could be white labeled. Thank you!