Trying to remember off the top of my head (if it doesn't work, let me know and I'll do a more thorough check):
Once the punk starts accusing you of being a nark, you can go and speak with with the "bored drunk" in the bar (he is the second one from the right at the bar counter, you can pay him to go get drugs for you

Let me know if that does the trick for you.

Why not getting a coke? Where could one get a coke?

Beats me. I can´t find a coke although there are millions of vending machines in the game.

"Coke" in this situation is referring to the drug, not the soda :)

Cocaine - yes

BTW, I would love sort of an achievement guide.. to make that a little easier I'm in a second of (no idea how many, but the game is good) x playthroughs, some achievements seem to lurk in arcs, I don't see to reach now

Originally posted by sylviakotulla:

BTW, I would love sort of an achievement guide.. to make that a little easier :shibuya: I'm in a second of (no idea how many, but the game is good) x playthroughs, some achievements seem to lurk in arcs, I don't see to reach now

If there are specific achievements you're stuck on I'm happy to see what I can do to give you step by step guidance on what to do to unlock. I can take a look at modifying the current walkthrough to highlight where each achievement sits, though it might take me a while to find the free time to do so :(

But that would be wonderful! I cannot say which achievement exactly, as I'm discovering the different branches of the story and thereby even stumble over the one or other ! But sort of a red line, that were nice. There are so many options

Originally posted by Deep Taiga:

"Coke" in this situation is referring to the drug, not the soda :)

Yes found out after I sent this. XD
Then I knew what to do.

Now I managed to lay my hands on the medaillon (all keys, medaillon - great) and: when can I give it to Grace? The game always says no....

Originally posted by sylviakotulla:

Now I managed to lay my hands on the medaillon (all keys, medaillon - great) and: when can I give it to Grace? The game always says no....

you'll automatically give it to her when you reach the end of the game to unlock the true ending once you have the medallion

Yes! Experienced this now - the true ending is done. But there are a lot of other ways and options to experience - even the failures are interesting. And, I had such a feeling about the story, this momentum of 'he cannot succeed, as Grace is already dead'.