Why TomCat 8 can't work on my Ubuntu 15.04 system?

I have installed TomCat 8 on an Ubuntu 15.04 system using this command:

sudo apt-get install tomcat8 tomcat8-docs tomcat8-admin tomcat8-examples

So I have that the installation directory is:

/usr/share/tomcat8/bin

So I enter in this directory and I perform this command to start the server:

sudo ./startup.sh

And I obtain this:

andrea@andrea-virtual-machine:/usr/share/tomcat8/bin$ sudo ./startup.sh 
Using CATALINA_BASE:   /usr/share/tomcat8
Using CATALINA_HOME:   /usr/share/tomcat8
Using CATALINA_TMPDIR: /usr/share/tomcat8/temp
Using JRE_HOME:        /usr/lib/jvm/java-8-oracle
Using CLASSPATH:       /usr/share/tomcat8/bin/bootstrap.jar:/usr/share/tomcat8/bin/tomcat-juli.jar
Tomcat started.

So I think that the server is started.

The problem is that if I try to open this URL http://localhost:8080/ into a browser I obtain the error message Connection failed (I don't know it it is the right translation in English language because I see it in Italian language).

If I try to open this URL ****http://localhost** (without the 8080 port specification) I obtain the Apache 2 web server information page (I used it for some PHP website).

If I try to perform the TomCat shutdown I obtain this error message:

andrea@andrea-virtual-machine:/usr/share/tomcat8/bin$ sudo ./shutdown.sh
Using CATALINA_BASE:   /usr/share/tomcat8
Using CATALINA_HOME:   /usr/share/tomcat8
Using CATALINA_TMPDIR: /usr/share/tomcat8/temp
Using JRE_HOME:        /usr/lib/jvm/java-8-oracle
Using CLASSPATH:       /usr/share/tomcat8/bin/bootstrap.jar:/usr/share/tomcat8/bin/tomcat-juli.jar
lug 16, 2015 2:13:35 PM org.apache.catalina.startup.ClassLoaderFactory validateFile
AVVERTENZA: Problem with directory [/usr/share/tomcat8/common/classes], exists: [false], isDirectory: [false], canRead: [false]
lug 16, 2015 2:13:35 PM org.apache.catalina.startup.ClassLoaderFactory validateFile
AVVERTENZA: Problem with directory [/usr/share/tomcat8/common], exists: [false], isDirectory: [false], canRead: [false]
lug 16, 2015 2:13:35 PM org.apache.catalina.startup.ClassLoaderFactory validateFile
AVVERTENZA: Problem with directory [/usr/share/tomcat8/server/classes], exists: [false], isDirectory: [false], canRead: [false]
lug 16, 2015 2:13:35 PM org.apache.catalina.startup.ClassLoaderFactory validateFile
AVVERTENZA: Problem with directory [/usr/share/tomcat8/server], exists: [false], isDirectory: [false], canRead: [false]
lug 16, 2015 2:13:35 PM org.apache.catalina.startup.ClassLoaderFactory validateFile
AVVERTENZA: Problem with directory [/usr/share/tomcat8/shared/classes], exists: [false], isDirectory: [false], canRead: [false]
lug 16, 2015 2:13:35 PM org.apache.catalina.startup.ClassLoaderFactory validateFile
AVVERTENZA: Problem with directory [/usr/share/tomcat8/shared], exists: [false], isDirectory: [false], canRead: [false]
lug 16, 2015 2:13:35 PM org.apache.catalina.startup.Catalina stopServer
GRAVE: Catalina.stop: 
java.io.FileNotFoundException: /usr/share/tomcat8/conf/server.xml (File o directory non esistente)
    at java.io.FileInputStream.open0(Native Method)
    at java.io.FileInputStream.open(FileInputStream.java:195)
    at java.io.FileInputStream.<init>(FileInputStream.java:138)
    at org.apache.catalina.startup.Catalina.stopServer(Catalina.java:427)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.apache.catalina.startup.Bootstrap.stopServer(Bootstrap.java:400)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:487)

So what could be the problem? What am I missing? How can I try to fix it?

Tnx