First the router does not make your internet slow. The router can handle speeds far greater than your Internet speed. It handles several pcs on the LAN side at 100 Mbps; your WAN side handles the feed from your ISP which is not likely over 10 Mbps.
Secondly, if you feel you are seeing a slower speed, measure it. Do not assume a download from some web site is a measure of speed. Most downloading servers do not deliver anywhere near the max available speed; in fact they throttle back to be able to feed several users and as the number of users increases, the speed per user drops.
Thirdly, the Internet speed is the speed that is used by all users; if you have 4 users downloading large files, each will have approximately 25% of the total speed as it is spread among all users. When you run a download test, all other users must be off line.
Fourthly, I note that you have a wireless router. I suspect you have not implemented all the security steps available to you and freeloaders have hacked in. Install and implement rigid security and this keeps freeloaders from getting in. My guess is that this is the real cause of your apparent slow speed.
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