Hello @BGT68 and welcome to the Community!
Having more than one security solution installed on the device will cause slowdown, incompatibility issues, and the normal action of either one of them is not guaranteed. This is why it is recommended to remove any other antivirus programs you may use before installing Bitdefender.
Symptoms may include but are not limited to degraded performance, system crashes, and software errors, since both programs will compete for the same resources.
I hope the information is helpful.