Did you initially have to log into the router to enter your broadband username and password ?
Opening a command prompt and entering
ipconfig /all will display the Default Gateway which is the router's log in URL address.
Can you post the make and model of the router and then we can have a Google to see if anyone has posted user instructions.
It doesn't matter what language a Google link is in as we can use Translate with Bing.
If you are free to do so and you have alternative broadband suppliers, I would suggest that you Google to see if they have a forum and check out their most common complaints to determine that you're not going to be going from bad to worse.
Normally threatening to leave a supplier can sometimes motivate them to take some remedial action.
Did you try inSSIDer3 to see if you could change to another channel ?
While this could help with a WiFi connection, it won't do much if what you have coming down the line is poor.
When you wire up do you disconnect from the SSID so that you are just Ethernet connected as wiring up and having WiFi enabled as well wouldn't determine if Ethernet is any better.
With ADSL your connection quality and speed are determined by the length and quality of cable between you and the exchange.
As a rough guide, in the router stats look for the Downstream Attenuation and divide that by 13.81 and that will give the answer as kms.
To power cycle a router you switch it and your computer off as well as disconnecting all cables.
After it has sat like that for a couple of minutes, connect all of the cables and just switch on the modem if separate to the router.
Wait until all of the lights are back on and solid then do the same for the router and then switch the computer back on.
You can check your speed at
www.speedtest.net and doing this before and after the power cycle will show if there has been any improvement, but I suspect your problems are due to either your ISP's equipment at the exchange or the quality of the cable between you and the exchange if your Downstream Attenuation isn't over 60dBM.