3. Check the flush handle or the flush button of the toilet
It will not be possible to flush the water if the fixed nut on the flush handle is not tightened or the flush handle is broken. Therefore, in order for the water from the toilet to flow down strongly enough, you need to tighten the nut or replace the lever or the flush button if necessary.
4. Check the toilet vent system

If you do not know how to check the toilet vent, please contact a professional for early support.