What does the error tell us?

Problemereignisname:  BEX64
Fehlermodulname:  StackHash_756f
Ausnahmeoffset:   PCH_A3_FROM_GTAVLauncher+0x00000000000A5B29
Ausnahmecode: c0000005
Ausnahmedaten:    0000000000000008

0xc0000005 is an exception of type (memory) Access Violation, meaning that the game tried to access memory that did not belong to it ^[1]. This might be a software error (bug) in the game itself, or in one of the libraries it uses ^[2].

This particular error is probably raised by DEP (Data Execution Prevention):

A user-mode DEP exception results in a STATUS_ACCESS_VIOLATION (0xc0000005) on Windows systems. The first parameter of ExceptionInformation that is located inside the EXCEPTION_RECORD structure contains the type of access violation that occurred. A value of 8 for ExceptionInformation[0] indicates the access violation was an execution violation.

Note that this (8) is the value of your Exception Information (Ausnahmedaten).

How do we fix this?

Because this is a software error, the usual course of action is to wait until the publisher updates the software. This is the safest course to take, but may take a few days or weeks.

Another option is to exclude this application from DEP. However, because the DEP error is a symptom of the problem, and not itself the problem, there is no guarantee that adding an exception will resolve your problem.

From the Wikipedia:

These problems may be prevented by disabling DEP, but this increases vulnerability of the system to malware. DEP can be turned off on a per-application basis, or turned off entirely for all non-essential Windows programs and services. Microsoft recommends that DEP not be globally disabled where an application malfunctions due to incompatibility with DEP. Instead, the supplier of the offending software should be contacted for an updated version that does not violate DEP; until the problem is corrected DEP may be disabled on an exception basis for the offending application only.

^{[1] ... or that was not marked to be so accessed, e.g. trying to execute code from memory not marked as executable.}

^{[2] However, Windows was unable to determine where exactly it went wrong, which is why it took a "Stack Hash".}

I answered a similar question recently. It is one of a few returning player exclusives. That means you have started playing on the previous generation (Xbox 360, PS3) and moved over to the current generation (Xbox one, PS4). There is no other way to unlock the Duke o Death. Guides that tell you how to unlock it, but don't mention "returning player reward" quite likely assume you have got the content already, and therefore must already be a returning player.

What I can not confirm is whether you can bring the content in if you start the game on a new console and then play it on an older console.