The TYPO3 Configuration shows error

Hello guys,
I have the TYPO3 CMS but it has weird behavior. For example no root node is found. Then now there is an error that throws up with the message saying there was a mistake.
Below are also other error I encountered:
error code, e.g. 1247043365
description, e.g. “Currently your TYPO3 installation seems to have no site defined, please create one by using the Manage Content module.”

Error message:
Ooops, it looks like we’ve made a mistake, something has gone wrong with this request.
An administrator would call this error:
T3.017 – TYPOscrip template is missing.
