Ovh.com domain: redirect from IP address to domain name

I have raspberry pi web server in my home. It is running on apache2. Router ports are redirected and that is ok.

That web server is accessible from internet by entering my external IP address eg. www.olanside.com

I want to have a domain name like www,mydomain,com rather than IP address so I bought a domain on OVH.com

Then inside ovh domain panel, I set up a redirection: www,mydomain,com to 5.123.123.123

It does not work, www,mydomain,com showed some OVH welcome message.

Then I've read something about DNS servers so I've checked my router DNS addresses (1.1.1.1 and 8.8.8.8) and inserted them into ovh dns panel as well.

Now webpage is not loading at all (no ovh welcome message).

How do I set it up properly?

Thanks for help