Need an iOS and Android developer to modify app

Need a modification and improvement to an existing app. This change will affect the default opening main screen and modify the algorithm for the uploading of video from the camera. We want the video to get compressed at the database or app level to speed view-ability of the video by the users. Additional modification to the camera picture sizing is also required. We want the app to open to the latest video posted similar to what occurs with Tik Tok. Must have experience with video and camera useage in apps.
You can download the existing app from Apple App store or Google Play. Chatkazam is the name of the app.