Issue with Wifi connectivity only during the evening timings

I am facing this problem from last so many days, I am able to connect to a wifi all day long. But only during the evening time, I fail to do so.

The difference is, all day long it is only 3-4 devices are connected to the wifi. But, during evening times it is around 10-14 devices are connected to wifi.

However, I tried restarting router n number of times but even after doing that, I am not able to connect to wifi.

I also tried updating maximum lease time of dhcp

But if I switch on my laptop, next day morning, it works perfectly fine. But again during evening it fails to connect.

Please help me, if you can resolve this issue. I am using D-Link - DIR-615 router