Charging the Iphone 12 Pro Max_

Good afternoon from Greece.

I'd like to ask you , if i can charge my brand new , iphone 12 Pro max with my chargers from my previous phone which was an Iphone 6S.

I think that , there is a 5 watt power .

I know that all these phones , charges better with charge of 18 or 20 watt .

And all these chargers , are charging the device very fast.

But in case that I want to use my previous , 5W charger....

Will there be a problem with the device?

Thank you in advance