You can't start the resource because some activities require players and resources to have admin group, which you can specify in the ACL.
First, open your MTA server folder, then open the following file with a code editor or IDE: server > mods > deathmatch > acl.xml.
To give yourself admin rights, look at your nickname in the MTA:SA client, then insert a new line in the opened file under the admin group.
It should have the following content: <object name="user.yourNick" /> (Replace yourNick with your own nickname.)
After that, save the file in the code editor or IDE in which you opened it.
For the changes to take effect, enter the following command in the server console: "reloadacl"
After that, connect to the server and register yourself as a user.
Type /register [nick] [password] into the console or chatbox.
Since you are using your MTA nickname, you only need to log in with the specified password, so the syntax of the login command is: /login [password]
If you have done everything correctly, you should be able to use the "start" command after logging in.