need part time permanent remote freelancer

Hi. we need part time permanent remote freelancer who can work on our existing project to fix bugs, add features etc. this app is built for E-learning one on one audio, video sessions just like skype. this app has: audio, video, screen sharing, conferencing , ios native and android native apps. it is built on webRTC, Node.js , angular.js , asterisk, xcode, callkit, android studio. we need someone really expert in above skills. and you should have some apps ready similar to above skills.