How to make plywood balcony surface waterproof?

Thank you Karsten, for your comments on the roofer problem. As mentioned above, I had already realized that I need a conversation with the executing craftsman before the work begins. When life-threatening behavior is unjustly attributed to me, and the deletion of the thread is repeatedly demanded in outrage, I do not find that kind, but inappropriate. A note on your concerns might have been sensible.

If I am accused of life-threatening behavior without reason, and multiple times outraged calls are made for the thread to be deleted, I do not find that nice, but inappropriate.

I did not call for deletion, but for closing the thread including notes about what is dangerous (which is by the way usual elsewhere for similar things). Instead, my posts were deleted + I received a warning for my request. No wonder there is hardly any traffic in this forum anymore and many gather in other forums where much more is going on. When I was here under another name, there was much more activity and there were many more active participants.