E34 525Tds cold start (-26°C)

Hi. I added this comment not to write the same answer multiple times.
1.) Yes, I could turn the radio off, but it doesn’t consume too much power and during starting it is off anyway because of unloader relay, so I don’t think it would helped much. Everything else was off.
2.) Yes, it was too risky to keep cracking for so long, but battery was old (charging whole night) and maybe if I try to start more times, it would not have had enough power to start cranking again.
3.) Why I didn’t start immediately after glow sign goes off? Preheating takes longer then sing is active. So, I was waiting until preheating is finished completely. It is normal behavior of the ECU and preheating unit.
4.) Glow plugs were unknow condition. This had probably a bad influence.
5.) You don’t need to be rude in comments.
Anyway, I was able to start, not ideal start, but many cars weren’t. Starter keeps working. Battery and glow plug were replaced.