Problems with a back-to-back MOSFET dimmer for 230VAC
On the right of the diagram swap live and neutral. This is a safety thing although you should never assume neutral is anywhere near earth it is likely to be lower than live. Now your switch is floating on the neutral line not the live.

The drive voltage for your gates has to float referenced on the source connection between Q5 and Q6. Short out R19.

Remove the bridge rectifier it is not needed instead connect D7 to the point that you have labelled in your current diagram as Neutral_230VAc. The ground end uses the body diode of Q6. 

Here is a rough diagram component values same as yours