Error 500 when accessing domain administration

[Mihai71]

Hi, I'm new to this web sector and I was hit by two problems:

1. when installing on the purchased domain and hosting I received a 500 error and it was blocked installing and then I resumed from the previous step. After completion the store did not open in front, in the back I saw all the applications but I had not created index.html. If we access the domain www.shop-romania.ro I get the message "Page in preparation" and the header of the hostinger, Ionos.

2. I found on the forum some information about Configuring and using Prestashop and I set it in the Preferences section -> Traffic & SEO to 301 Change after activating the store which blocked me with the error "The page does not work
Currently, www.shop-romania.ro cannot process this request.
HTTP ERROR 500 "
Can anyone bring me to light? I think I made a fool and do not know how to reactivate the administration of the domain www.shop-romania.ro/admin8721

Thank you in advance

Edited April 6, 2020 by Mihai71 (see edit history)