why theme always "forgets" what I already did do?

For example: I wrote something in section 1.
I made the size of the letters, used html codes etc etc.
I saved it, seen my page, everything was ok.
I went to section 2, do the same thing.
Went to my page again, section 2 was okay, but section 1 was like I just wrote the sentences there, but the letter sizing changes and html changes all dissaperaed.
Again, there is some photos in the theme about flowes and I dont know. I changed that for the photos of my businness. I went to see my page, everything was like I did.
Then I went to change the adress in the footer.
When I went to see my page how its look like, all my photos disapperad, I saw the original photos in the theme.
Same thing with section 4, I changed the stuffs there twice, now I changed the footer, it disappeared too ??
I want to use this theme cause its exactly what i wanted, but this way I cant use it ??