I never store any files in C drive. Cannot trust Windows updates which start automatically and then no option to stop or delay. Just wait until it does whatever the update intended to.
Using Dongle for Online gaming is not recommended. Even if we ignore the latency, the data charge is higher than DSL/Cable.
Can't you ask Telkom to replace the old copper cable with Optical Fiber?
Any possible virus infection? Can you perform a full system scan with any AntiVirus program?
Or press the reset button. But I think the issue is due to virus infection if there is no Windows update issues.
If the LED light for the Internet on the router is off, the problem is at ISP side. You should contact them. Are your neighbors having Internet connection from the same ISP face this issue?