what do you think about the installatio, maintenance, and testing of asterisk? in these 3 pionts where do you found more troubles?

Instalation of asterisk is very simple.
make install
make samples

There the install is done

the intial config can be difficult but there is loads of documentation on this, As for testing load, there are few tests to do this but it is fairly simple to generate calls in a loop till you reach your max.