Licensing desktop software, how to word the license for the commercial version?

So, I am working on an application to make devops-like best practices accessible to non-sysadmin types. It's most likely going to be licensed using the Parity Public License from https://licensezero.com, which means if used in combination with other open source software it can be used freely. If used with proprietary software, people will have to buy a license.

Ignoring -- for now -- the much harder problem on how to market something like that, esp. to fellow developers, I'll also need a commercial license text for the unlikely case somebody will actually buy one, which states what is allowed, and what isn't. The LicenseZero website actually has a private license template, but that allows sub-licensing, which is something I don't want.

So, I figure I need to talk to a lawyer. Can anybody on here recommend one that is specialized in that sort of thing? I'm in Berlin/Germany at the moment, so a German one would probably be best, but maybe it doesn't matter? Or does anybody on here know of services that can create a fairly bullet-proof license text for me?