You can’t have multiple java’s utilised by installing each one without some extra work.
In server.config you can populate java_binary with the absolute path to the java binary of a certain version.
e.g. I have extracted java 11 to /usr/minecraft/java/jdk-11/
if I recall correctly the absolute path to the java binary is
/usr/minecraft/java/jdk-11/bin/java
You can download a version of java 11 from
Also, a lot of these questions and trouble shooting has been talked about in the other similar threads, please research yourself and see if you can figure this stuff out.