by Mr White »
Sun May 12, 2019 8:12 am
The old switch is 2 gang (It has two buttons) your new switch appears to be 1 gang (Only 1 button) so that is your first reason you can not use it. The second reason is if you look to the left there is a terminal marked N in (Quite common on wifi switches) UK lighting in the majority of cases does NOT have a neutral at the light switch, so that is another reason you can not use your new wifi switch.
As for how do you put the old switch back, that is a case of trial and error as there is no definitive colour coding for two way switching (Which is what you appear to have as you have 2, 3 core and earth cables) You could look at the other switch that operates the same light and see how that is connected and duplicate it at this switch.