@VVe,
i would recommend looking around the forums,as there are many possible solutions.
I would first look at your QoS settings; try setting the speed manually to what you expect to receive from your ISP or above. The benefits of QoS are most seen on sub-300mbpps connections.
Try changing your DNS server to a common service such as Cloudflare or Google, some users have reported that this change can dramatically increase throughput.
On your PC, I would recommend looking to see what the connection speed is listed as. It is not uncommon for PCs to not negotiate with a networking device correctly. You can force the Port Negotiation Speed or view the current settings from the adapter options menu. Also make sure that the laptop's network card is capable of receiving the speeds.
When you are connected the 5Ghz wireless network, does the speed increase, or does it still appear as though the bandwidth is limited?