First, my skype didn't have sound effects so I uninstalled it then I reinstall the skype. The sound effect still not working so I downloaded the new version of skype ( beta one), I installed it then the sound effect still not working so I download the old version of skype then install it. The sound effect works but I lost all of my contacts and lost all of chat history. The chat history is really important for me. May you please help me to restore my chat history? Thank you.
Sorry, but it's very unlikely you'll be able to get your chat history back, because in uninstalling Skype you probably removed all of the associated data. Assuming you have Windows, you can try and look in Skype's directories under Program Files and maybe Application Data (if you have an older version of Windows).
That said, if the chat history is really THAT important, you can ask the person you had the chat with to send you the transcript.