[TYPO3-english] Calculated absolute path to typo3/sysext directory does not exist.

[Mikael Nazarenko]

Hello everybody! I am only started learning typo3. I have problems. 
I have installed typo3 version 7.6.16 after that I installed templavoila version 2.0.4
Now I see follow error in back-end on page section:
Calculated absolute path to typo3/sysext directory does not exist.

Something in the main file, folder and link structure is wrong and must be fixed! A typical document root contains a couple of symbolic links:
* A symlink "typo3_src" pointing to the TYPO3 CMS core.
* A symlink "typo3" - the backend entry point - pointing to "typo3_src/typo3"
* A symlink "index.php" - the frontend entry point - points to "typo3_src/index.php"

I looked this forum and other places. I saw somethink solves but it did not help me. I do not now how to fix this problem. 

I really hope for you all ! 

Thank you all in advice