How to get user side SSL certificate from android app?

Question

Android

There is an application for Android. It accesses the internet and gets the X channel streaming playlist. The stream is encrypted with AES-128 bits. There is a link to the key in the playlist, but it is impossible to get the key from the PC, because it swears that the certificate does not match on the user side (SSL connection).
I decompiled the application, but due to inexperience I could not find anything there. Tried to sniff the traffic, but also found nothing.
I ask for help or advice - how to get and replace a certificate in order to download a file to decrypt a video stream.