According to this discussion you can only officially get a better starting block with a marathon time, but not with a half-marathon one:
https://forum.runnersworld.de/forum/...erlin-Marathon
They go on to say that some people will let you move to a different block if you show proof of HM time when you pick up your number and stuff, but some people won’t. Seems to depend on how German the person you talk to is
One person claims to have run <3:10 from the last starting block.
If you haven‘t registered your time yet, some people claim that you don’t have to show proof for having run it and the website asks people to be honest, doing that is still an option, telling them you PB ist 3:14 or something seems to be your best option.