The chimney is not drawing smoke

Hello everyone,

we have a small garden house (concrete house) with a gable roof. In it, there is an open fireplace with a chimney above it. The problem is that the chimney simply does not draw. The room always fills up extremely with smoke and it is almost impossible to grill on the fireplace. I have attached a sketch and I hope that you can see how the area is constructed.

Notes:
- Maybe the wood funnel is too high and should rather lead directly into the hole, so that no smoke can accumulate between the wood funnel and the chimney
- The chimney at the top is possibly too short because it is a bit smaller than the roof ridge (it is not clogged)
- There is enough air in the room
- The diameter of the chimney is possibly too small? Max. 10cm
- Maybe the distance between the wood funnel and the fireplace is too high (probably larger than in the sketch)

Can someone help me and say what characteristics might be causing the chimney not to draw the smoke out and what measures could help?

Thanks in advance

How high is the chimney? For a wood stove, 3.5m is usually enough to get sufficient draft. For an open fireplace, it has to be significantly more. A stove fitter or the local chimney sweep can help. The latter must also approve the system. DIY without professional advice is out of the question; smoke is not only unpleasant but also poisonous. Carbon monoxide kills quickly. So don’t do that nonsense and get help from a planner who knows the subject. It doesn’t cost a fortune, botched work can cost you your life. In summer, you won’t really enjoy the fireplace anyway. As soon as the indoor temperature is lower than the outdoor temperature, the pressure conditions become so unfavorable that even a tall chimney alone won’t be enough. For this there are electric smoke extraction systems (a kind of fan), which are placed on top of the chimney.

Thank you for the response!