Just using smart manager should not have touched your files unless you for some reason actually selected them to be deleted, is that what you did? Without a backup of those files somewhere like cloud storage or a computer, they are gone. There is Samsung cloud and some other places you can check https
/www.samsung.com/au/support/mobile-devices/how-to-find-samsung-cloud-recycle-bin/
There are several undelete apps but most are ones you need to pay for. You can try Recuva I think they have a free one you can try.