change theme

Hello,

Two things which are linked :

I created my website on ‘Hedy’ theme but wanted to see/how it look like if my website is on ‘Twenty Fifteen’ but it seems we can’t do that. We can but we have to re-create/redo everything, menus, pages, etc…. is that right ?

I also switched between ‘Hedy’ theme and ‘Hedy child’ but I can’t see any difference int he lay-out ?

My issue is I’d like to create a static page for the homepage instead of a blog but I can’t find the way to do it on ‘ Hedy’ theme ? Not possible ?

Many thanks for your time and help.
Donatienne.