Migrate from a wordpress theme to another

Hi all, I ask your help because I don’t know how to migrate Kallyas wp theme developed by Hogash to Sydney Pro theme.
I will lose all my content? Thank you and hope someone gives me an advice, please!

Hello,

I will lose all my content?

You shouldn’t lose your posts and pages but you will lose theme settings. And most likely you will have to recreate your home page using Elementor. You can try to do it in a staging environment first, here is a relevant tutorial:

Please feel free to ask any other questions that you might have.

Kind Regards, Roman.
aThemes Support