If you connect directly to the modem/router (the speedtouch 5x6 is both modem and router) and do not have the issue of your connection dropping, then you can safely assume that the modem is not the problem.
If your TP-Link router is regularly dropping both wired and wireless connections simultaneously, it could be the DC power supply to the router. The key there is "simultaneously". If at all possible, position the router so you can observe it. When you experience the disconnect, look at the router and see if it is power cycling. Typically, when the DC adapter goes, this power cycling occurs ever minute or two... but there could be longer delays between cycles. It could also be the router itself, as opposed to the power supply.
If the router is dropping the wired and wireless connections independently, then it again is most likely the router, but it might not be a hardware issue. It could be a settings issue, or even a DDoS attack hitting the router.
So... if you have another router, replace the TP-Link one for a time. Otherwise, watch and see if it power cycles.