Issue with css table with module builder

I am now trying to use the module builder as much as possible for module creation but I have an issue because all css features on table are not implemented when I use the module builder

for example
when i put simple simple css class it works well for example
.important {
font-type: arial; color: red; font-weight: bold

but when I want to make css on tables, then nothing works anymore …
for example just with


i am not good at css but this is very strange, because it worked without module builder so maybe something is implemented already for the tables … (datatables …)
then how to make my specific css prioritary ?

Thanks for your help