First I would get two steel supports to put in now, posts that are strong enough to carry the weight for the interim; you can probably rent them or buy them relatively cheaply. Check that they can carry a few thousand kgs. Put these in place. Next, I would remove the wood work, and order steel beams that fit into either side of the hole. I would plan on inserting a horizontal steel carrier beam. Mind, if you do not feel comfortable to do this by yourself, you will have to get a professional to do it, after all, you don’t want the floor above to collapse.

Removed by mod

Removed by mod

I was all-in, because I misunderstood the phrase as meaning “prohibit all games in which people are killed”. Man, do I feel like an idiot.