Crazy lost in my setup

Hi there,

Well I have done a website with wordpress a local by flywheel.
I was really happy with my design and the I have buy a server place and a web address.
There I tried to import my wordpress into the server. I followed a tutorial how to import with SQL and everything.
They told me in the tutorial to change my wp-login.php for relink my stuff. I have done and it was working.
But after some manipulations I found my self completly lost.
So I deleted everything on my server web (what I uploaded with ftp) and tried to start to the beginning.
But know I have change things in my wp-login.php and now everythink doesn’t work !..
I really don’t know what to do. I am affraid to lost all my wordpress design, but I still have my local files everything, so I think it must be somewhere.

When I try to restart my local website I have this message : Error establishing a database connection
So I must put the first logs I had at the beginning. But I can’t remember…

Well I really lost.

If someone could help me ?