Hi
Can i install asterisk in container using a ready docker image?
Note, I only use SIP for calls.
Can you? Yes. Does the project provide a Docker image? No. Should you do it without an understanding of Docker networking, SIP fundamentals, and Asterisk SIP configuration including networking? Probably not.
I think you missed out “Can I get help with such a setup if I need it? Maybe,
but only after providing a lot of detail about your specific setup.” 
Antony.