Thanks for the explanation!

Since we are on the topic of signal… im not tech saviie but i have read lots of blogs and people about how secure is the signal protocol. My question is … how can i be sure that the protocol is implemented as the open source code shows? Please correct me if im wrong but from what i read on their website the apk they provide has the capability to update itself at anytime. So what stops them to change how it works with an update? is it posible to build the apk yourself and stop the ability to update?