reinstalling mac os after data erasure

hello! I have an old imac from 2014

I erased all the data through the disk utility, then I had to reinstall the mac OS. for the tenth time, the Sierra mac os is loaded, but after it says "0 seconds left", it shows "405 seconds left" or "5 seconds left". and so the download can stand overnight or longer. the computer is connected to the Internet, I erased the necessary volume according to the instructions.

I have already rebooted the computer completely several times, started downloading again, but nothing helps

how to fix it? thank you in advance