The receipt from your online renewal won't protect you if you get stopped. Traffic officers check the physical document, and if your license shows as expired in the system, technically you're driving without a valid license. The fine is hefty - over 500 euros - and you could potentially have other insurance issues too.
That said, delivery of the physical card after an online renewal often takes forever, and a lot of people end up in this situation. The smartest thing is to contact the driver portal or the relevant office to check where your application stands and whether there's a way to speed up shipping. Some regions let you pick it up at their counters, others give you provisional documentation you can carry with you.
In the meantime, if you absolutely have to drive, do it only when it's essential and bring all your paperwork with you (receipt, online confirmation, everything). It's not a guarantee, but at least you're showing that your application is in progress. Ideally you'd put off any non-urgent trips until the actual document arrives.