Hai friends I am going to tell you the most interesting app that is qoura which make you to learn the facts about which you choose and give the permission to you to ask question and send your question to the teacher or friend or any other people and they respond back to you about your question and ask there own question that you can answer and when you want to learn something it well help you to give more better answers for your question and you can follow many famous person about there topics and ask them qoura is the bestapp to update your knowledge I tid it and I gain my own my knowledge and I recommended you to use its a best one app try it