is there a way to set priority of the android phone app, for example to have the android app ring at a later time or if the desk phone was not answered at a set amount of time?
Is the Android phone app and the desk phone on the same extension? If so, no it is not possible to prioritize which phone should ring first. Both phones will ring simultaneously, [This is known as SIP Forking]
On the other hand, if they have different extensions, you can set Forwarding Rules for unanswered calls to ring another extension when the other phone is unanswered