it makes some effect for bitcoin prices or not if 1 of the big pool closed?
No. Mining is affected directly by the price of bitcoin. The price of bitcoin is not directly affected by mining.
yup, if the bitcoins drops again most miners would be forced to close
Some have huge margins so it would just mean they are not making much money out of their investment or suffering a small loss but most will keep mining hoping for a higher price in the future.
If the price stays relatively low mining farms will slow down investments and not replace hardware; there will be less new farms and they will be smaller