where is the diagram?

the external switch can only function as a toggle. if the sonoff is on, it will toggle to off when you flip the switch. and vice versa, if sonoff is off flipping the switch will turn it on.

you can use sonoff app to toggle the switch. additionally since you have the wireless button, you could also create automation in sonoff app to toggle the switch upon click of the wireless button

rewiring the switch will not solve anything. the hard switch will always act as toggle switch.

I'm assuming you have successfully configured both your sonoff mini and wireless button in ewelink apss.
1. Go to ewelink app, go to scene tab, click on the + button at upper right corner.
2. Add new trigger, select smart device , then select your wireless button, and select single click, click save multiple times until you arrive back to adding actions.
3. Add new actions, select smart device and select your sonoff mini, then select reverse(toggle) , then click save multiple times until you save the automation.

Now when you single click the wireless button, it will toggle your sonoff mini switch.
As always, the physical switch on the sonoff mini will also toggle your sonoff mini switch.

sorry i have no experience with that model of sonoff