Dear Kolega2357, Welcome to MediaWiki.org!
Yes, welcome! This site is dedicated to documenting the MediaWiki software, the software behind many wikis, including that of Wikipedia and the Wikimedia Foundation projects.
Please, take a look at the following pages. They might prove useful to you as a newcomer here:
If you have any questions, please ask me on my talk page. Once again, welcome, and I hope you quickly feel comfortable here, and find this site useful documentation of the MediaWiki software.
Thanks, and regards, GeorgeBarnick (talk) 19:08, 20 May 2014 (UTC)
Hey, just wanted to point out that it's not necessary to undo revisions to Project:Sandbox like you did here, as we have a bot that will automatically reset the sandbox every so-often. Thanks! :) GeorgeBarnick (talk) 19:08, 20 May 2014 (UTC)