Why does my sourdough pushes like a roman legionnaire?

Hello everybody, complete beginner here. I am playing around with sourdough for fun and i am loving it, but i have a small problem.

I am doing 24h Poolish starter and mixing it to make a 24h cold raise in the fridge, but even in my last attempt in which i reduced the ammount of starter to almost nothing and used ice cold water to ensure the dough would stay cold, after putting in the fridge it rose in just a couple of hours. I am not adding any extra yeast to it and i don't understand why it raises so fast, can anyone enlighten me on why that is happening?

Also on an unrelated note i only have acces to a countertop oven that reaches a max of 230°C, so i guess bread like ciabatta is out of the question, but i have seen some focaccia recipes that are cooked within my oven range, so if you have a recipe you want to share i would be happy to try it, i need all the practice i can get :)

PS: i am not exactly measuring yet, but on my last attempt the stater was made with 1 Tablespoon of flour and enough water, and for the final dough i added 160g (i live alone so i make only small batches every 2-3 days to keep them fresh)