Yes, deleting deletes everything. You can of course simply create another account with another EMail-address (GMail allows you to
email@example.com) and play with that. You can possibly even talk with the Codecombat-Team (Nick for example) to find some possibility to carry over your subscription to your new account.
BUT you can also use your current account. When you start a level, open the menu and change your hero you can also select a new language. The editor will then be switched to the new language. You will get a lot of Syntaxerrors because your old code will still be there and most likely be not a valid code. There is sadly at the moment no way to backup code ingame, you would have to save every level-code in a text-file on your computer.
I do not recommend to start at the first level without the possibility to switch to later levels (aka a complete restart) as you already learned the basics. Other languages usually just use another syntax and differ only in more advanced topics (for example Pythons handy list-aggregation). So by skipping the first few levels you can get a good impression of the language quite quickly without fighting your way through the whole dungeon and forest.