Aly wroteIt could be from many factors, first it is 99% not because of your telephone cables since telephone cables are not sensitive to day and night cycle, there are several possible reasons:
1- Family members consuming the bandwidth which will cause the latency to become high (to double check this, simply when you are lagging log in to your modem, turn off the wifi only and see if the ping drops).
2- Congestion from DSP side, which means the infrastructure between your house and the ISP can be poor due to old copper wires or legacy equipment and will not handle high speed internet for the whole area you live in and therefore the connection will be poor during peak times (you can do nothing about that, you will have to wait for Ogero or whoever the DSP is to upgrade their infrastructure).
3- Congestion from ISP side, this happens when your DSP has a decent infrastructure but the ISP has a bottleneck from their end, their international links are operating at maximum capacity during peak times and cannot deliver the promised speeds for their customers, they usually cover themselves by telling the customer the speed is (up to x Mbps) and not dedicated ... you can also do nothing from your side to fix this.
In some cases you can have a combination off all above three reasons causing your high latency, your only hope is to change the ISP and hope your next one is better.
big thanks for this informative reply
i will try to call them or changing the cable because it was cut in the end and i connected it
if there is no solution i will change to local distributor
the coffe where i go to have 4 mbps and the ping rarely drop how much the connected clients are