Cannot edit the theme

Hello - I brought this theme and then paid to get the theme installed (which I have done before on a different website and had no problems).

Firstly, I couldn't edit the home page - I could and still can edit the menu bar - I could edit the footer but now not.
In the end I just made a different page the home but then realised that now I cannot edit anything.

I make changed - edit the text and then it just reverts back to the default template and shows me the home page!  I have had this issues for a number of days now and been on many forums trying to work out why!  I haven't added any plugins.

This is so frustrating - I now have a website which I cannot edit!!! 

Please can you help me