Hello,
At first sight, I do not see any problem with your site.
I was able to log in, but I can’t access Dashboard. Make sure that you set the administration role for the user and /wp-admin doesn’t any additional restrictions.
An error on your screenshot doesn’t tell me anything, could you translate it to English?
So, provide correct wp-admin access + temporary FTP access. Describe in more detail what exactly error do you have right now.
Regards