How to connect a Headset with separate Mic/Sound without USB

Hey fellow Macbookers!

I am doing some light gaming on my Macbook Pro Mid 2014.

So, I got the Sennheister G4me one Headset that has 2 jacks, one for the mic one for the sound. I bought a cable "Sennheiser PCV 05 Combo Audio Adapter" to use both Mic & Sound from the headset on the Macbook Pro: But, the mic doesnt work while using the adapter cable.

However, mic&sound worked using the cable on my Iphone: So its not a technical issue. So, question time.

1. Just to be sure: Can a Macbook actually use both Mic & Sound over the one existing jack?
2. If yes, whats the combination internal wiring of the "poles" (I dont know how to call it). Because the cable from Sennheister is CTIA and doesn't work.
3. If the audio-jack of the Macbook is OMTP, can I simply buy an OMTP/CTIA adapter which I plug infront of the Sennheiser adapter?
4. If 3) works: Someone wrote left/right sounds are switched while using an OMTP/CTIA adapter: True?

I did use an external USB soundcard, but had issues with background noise & the general sound quality. And it broke. So Id really prefer a cable solution 🙂

Thanks a lot for the help,

Tobi