My Network Crashes Suddenly

Since 4 days my network is suddenly crashing. It crashes everyday without any warning or something and there is no pattern so it sometimes crashes after 1 hour sometimes after 1 min and it happens like 5 or more times a day. Im using a Network amplifier, which is connected to my whole pc with an extension cable. So if i pull out the amplifier my whole pc turns off and after putting it in again my network works as usual until it crashes again. I also tried another amplifier and another LAN cable nothing works. The amplifier also works on my brothers pc normally.