All categorys are missing and posts have been uncategorized and all untagged.

Hello, last night I got a new theme for my website, I got it up and all sorted I then went to bed and woke up not long ago. Logged on my WordPress and opened a ta for my website and all the category’s are missing, I looked in the category section they were there but know there not.
Went in the post section and every post has been uncategorised and untagged. When go back to dashboard still says I have 9 category’s. Can anyone please help out much appreciated!