If these events are slowing down your router, that may be because it is using up processor time as it writes the events to your logs. Anything that uses processor power – event logging, QoS management, traffic metering – may cause slowdowns. Disable logging of DoS attacks and see if that reduces the problem. This does not prevent the router from protecting you from the outside world.
Then the usual boilerplate questions to eliminate some of the more common issues that crop up here.
What firmware version do you have on the device?
A number is more useful than "the latest". There may be newer versions, or "hot fixes", that do not show up if you check for new firmware with an app or in the browser interface.
If there is one it might also help if you told people the make and model number of the modem/gateway/ONT that connects this router to the Internet. Is it, by any chance, also a router, with a set of LAN ports on the back?
I ask because a lot of people turn up here trying to put a router behind a modem that is also a router. That can complicate troubleshooting.
