Reset after changes!

Hi

I am very new to the whole wp thing and I have absolutely no clue about CSS, HTML etc and I did not manage to set my hp up in 5min… Anyway, I am happy now but do have a (probably stupid) question:

Is there any way I can save my entire set up so that in case that something goes wrong I can simply upload my latest changes/theme?

Reason asking is that with my theme I have issues when undertaking certain changes. It happens quite often that when I try to do some changes (eg changing Fonts etc) that pretty much al my previous settings (ie logo etc) are reset! I am pretty sure it is a theme issue (mythemeshop.com.
However, woudl be great if there would be a way to save changes ie on my Computer.

Thanks