Using Malwarebytes EDR in a midsize company needs extra investment for web filter?

It seems you're looking for a content filtering solution specifically. Many products do that - sometimes features of your firewall (there may be a license or subscription to purchase), or a software solution that resides at the endpoints (it would be very important then to have it centrally managed). I prefer at the endpoint, so the policies travel with the endpoint and are in effect even outside the corporate network. I don't think this is the proper forum to make specific solution recommendations, but at the moment we're using Avast CloudCare, which has a category based content filter and it internet portal managed. It works well alongside MalwareBytes (Endpoint Protection in our case).

The MB web detections works great against malware, but maybe for the midsize companies, instead for a perimeter investment besides the firewall, the MB can add a web filter module to improve the best employees practice and productivity how to use the internet.

Another security layer, such as a perimeter firewall, can be used to address the web filtering and deter unwanted incoming traffic.

No, MB catches sites that have malware on it and will block the site.