Ok, I figured out how to stream, with one program, without any extra programs
The OBS Forum didn´t want to tell us, and I´m a bit ashamed, because the solution is that easy and I should know it, because of many other saves(of games) or other settings of programs work the same way
The 15 min limit was set via the Overlay of the program. (You couldn´t increase the number with the arrows over 900 and when you just write a number in it, that is higher than 900, it will be deleted after start of the stream).
So maybe any other guys, will also need a delay over 15 min. Here is the clue :
Go to your Appdatas=>OBS folder=>profiles=> set untitled.ini and now you should know where I wanna go
Change the current line:
Delay=1800 (For a 30 min delay).
And that was it
Like I said it´s only a limit in the overlay of the program, and the developers on their forum didn´t want to implement a "no-limit feature" right now, and I understand that also, because they explained it with the RAM problem:
NOTE: I have 12 GB RAM and the whole movie is saved temporaly on the RAM before it goes finally online (after the delay) , so I had like 50% "full" RAM while streaming (6 GB). So rather think about it
if you have only 4 GB or less for example. If you really need this, for a tournament game, you can also try to set the Quality a bit lower. I am streaming on FULL HD for a few months, so the size of those files is really big. Decreasing on 720p already saves more than 20% of Space AND Internetbitrate.