Change URL in General Settings

Ok, i guess i have to learn this one the hard way…

I realized that the URL structure on my site is not satisfactory and pondered on how to fix this.

After a while i realized that i did not change the settings under “Settings > General” to the proper domain in the beginning. It still had the kind of cryptic domain name at which my hosting company hosts the site. So i went on and changed this. Unfortunately the site just disappeared all along with my dashboard.

I updated the functions.php of my theme via filezilla and everything fortunately is back now.

Is there any way at all to change the general domain settings after the theme has been set up?

Or do i have to copy my theme files to my hard drive and reinstall the database as well as the newest WP?

Yes, i am a complete newbie! Please consider this… ??

Thank you so much! Ivy