I have a 2015 mac and I recently installed Manjaro on it since new MacOS was no longer supported and the mac was much slower running MacOS, but I have one problem. There is no sound, and since I have almost no prior experience with linux I have no idea how to fix it.
Welcome to the forum 
Providing system info would help others to see what your system looks like and suggest options:
There is some info on the arch Wiki about macs and sound, this might be relevant but not sure if it’s your model: