從今以後不再認真既英文係咩?????

to TAKE somebody / something SERIOUSLY
def : to believe that someone or something is worth paying attention to or should be respected.

eg : No one is likely to take Stephen seriously.
eg : Don`t joke with Fiona, she takes everything far too seriously.


never TAKE anything SERIOUSLY again ( 從今以後不再認真 )
eg : I will never take it seriously again.
eg : I`ll never take anything seriously any more.


Hope this might help.

從今以後不再認真既英文係咩?????

I will never, ever take it seriously after this.
or
I will no longer take it seriously again.

I will never be serious again.

I will not be serious about things from now on.