#!/bin/bash
s="Leonarfdsdy Dandfiel, Ingendfdfdfieur - Leon.inrombach, Hinderusen, 485,47580,SANKT VITH,BELGIQUE,0442345,2058560,FR"
sed -E 's/^([^,]*),([^,]*),([^,]*)((,[^,]*){7})$/\1\2\3\4/' <<< "$s"
IyEvYmluL2Jhc2gKcz0iTGVvbmFyZmRzZHkgRGFuZGZpZWwsIEluZ2VuZGZkZmRmaWV1ciAtIExlb24uaW5yb21iYWNoLCBIaW5kZXJ1c2VuLCA0ODUsNDc1ODAsU0FOS1QgVklUSCxCRUxHSVFVRSwwNDQyMzQ1LDIwNTg1NjAsRlIiCnNlZCAtRSAncy9eKFteLF0qKSwoW14sXSopLChbXixdKikoKCxbXixdKil7N30pJC9cMVwyXDNcNC8nIDw8PCAiJHMi
Leonarfdsdy Dandfiel Ingendfdfdfieur - Leon.inrombach Hinderusen, 485,47580,SANKT VITH,BELGIQUE,0442345,2058560,FR