Twitch streaming with PS4?

Here is my setup:

Ps4

Pc

Turtle beach headset

Webcam

Normal mic

OBS Streamlabs

Elgato

2 monitors

My question is: On one monitor I only hear the game sound and Playstation party chat and on the other monitor it's Streamlabs OBS. How can I hear the alerts. Can I use speakers for this? And what do I have to set at Streamlabs so that people only hear me through the normal mic and not through the headset? But my friends need to hear me through the headset.

I haven't dealt with it that closely for a long time since my setup slipped. By the way, I do it very differently now, but it's perfect for me.

You seem to have connected your headset to the PS4 via USB.
As far as I know you can't do anything worth mentioning so that you can receive audio from PC and PS4 at the same time and can also talk to it via PS4.
But you could e.g. Connect EarPods to the PC monitor and wear them under the headset. Would be too uncomfortable for me, but would work.
Loudspeakers would be too dirty for me, but would also work. You would then probably have to mute the desktop sound in OBS so that you don't hear it twice in the stream.

If you mean with the last question that the viewers PS4 can hear you through the headset, it might be difficult, but I would be surprised. I think that game sound and party chat (maybe you too) share the same channel.
I used to try around a lot and think about it, but I couldn't find a clean solution. If it should work the way you described it, you can put the question in again, but I doubt that it will be possible or easy.

But I have another suggestion that might work. Haven't tried it myself, but it sounds plausible.

Here is my current setup:
First, I only use Discord to talk to viewers or friends. Would be a lot better than PS4 Party Chat anyway. It won't be so easy if the friends just want to chat about PS4, sure.
I have 3 monitors, one for the PS4, one for OBS studio, Spotify, Chat, Event Log and the third one for Twitch Stream Overview and Discord.
I also use the Elgato to transfer the game from the PS4 to the PC.
I only use https://smile.amazon.de/gp/product/B00SAYCXWG/ headset for the sound (jack, not USB!). This is connected to an adapter with which I'm connected to the PS4 monitor and https://smile.amazon.de/gp/product/B005EHILV4/ mixer at the same time. The https://smile.amazon.de/gp/product/B01C05AL4C/ microphone (XLR!) Is also connected to this mixer. The mixer is connected to the PC via USB.
This means I can hear PS4 game sound over the headset and everything from the PC at the same time.
The microphone is only connected to the PC. I use this for the stream and at the same time for Discord.
The mixer is extremely recommendable because firstly it is not expensive and secondly you can easily change / adjust certain volumes.
Either whether and how loudly you can hear yourself speaking and, secondly, how loud you want to hear the PC sound without having to change the stream volume (you can adjust that separately in OBS or in the programs). Microphone volume in general, of course, and other things that I normally don't change as soon as they are set correctly. By that I mean the 3 buttons in the middle.
The fact that you can hear yourself talking on the mic is very advantageous if you have a headset that muffles other noises in the room (highly recommended because it is of higher quality). Otherwise you don't hear yourself well. Second, you can also better assess how well the audience understands you. This means that you don't tend to speak too much next to the microphone, etc. Because you then become (too) quiet for yourself.

So if you are more or less forced to talk to your friends via PS4 party, you could connect another USB headset or USB microphone to the PS4. In the PS4 settings you select this as audio input (microphone) and as audio output (loudspeaker) hold the monitor where your actual headset is connected and with which you can hear the game sound and hopefully also the voice chat. A separate USB microphone for PS4 would probably be more suitable. You could just put this second headset down next to you somewhere nearby or hang it up and use it as a microphone, but I think that it won't sound very clean at a distance.

As I said, I'm not 100% sure that this will work exactly like that, but I assume it (based on PS4 Party). If so, this setup is HIGHLY recommended. Compared to the past, I'm extremely satisfied with it, where I really like it

Oops, in the end I meant entrance, not exit.

If you are heard twice with these recommendations, because your own * audio INPUT of the PS4 is also transmitted, you can probably change that in the PS4 settings, but I would be very surprised that this causes problems.