Log in trouble

Hello,

I’ve asked a website designer to build-up 2 websites for me, and after 1,5 months, they send me back with nothing. So I decided to tried to build them myself. I have managed one website in a week. However, since I don’t know nothing about coding or anything with that language (I never work with www.ads-software.com before), I think I made mistake with this new site.

Now, I can’t open my admin section and I found this:
————
Not Found
The requested URL /a2015 was not found on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
—————
I don’t know what happend. Can somebody help me with this issue?
I really need a good support on this…
Thank you so much ??

This is my website: https://ayoberangkat.net/
And this is my admin panel: https://ayoberangkat.net/a2015

Bikuni