Hello, I really want to play on your server, but i cant´t join. here is screenshot of that error:

Have you ever thought of actually restarting your launcher ? xD
I've heard many people don't do it.
That almost always fixes this kind of issue.

Hope this helps
~ydna111

Sorry but i am not beginner on computer, of course i tried it. Many times.... But thanks for answering

Try restarting your computer and see if that will work, I have that problem sometimes to.

Do you have a lisence of MInecraft?

Yes, i tried to restart whole computer, but it didn´t work.  

Yes i have got license of Minecraft, but i think you can join without that licence