If you can hardwire to the router, your speed will about double.
Have you moved further away from the router, or is there anything metallic between you and it?
Signal strength may fall to a quarter if you double the distance.
The router should be strong enough. I used to be able to pick up the signal from my next door neighbour's!
Not knowing the password, couldn't get into it, although he did offer.
A metallic screen will effectively block the signal (Act as a Faraday Screen) Michael Faraday was so confident that he sat inside a metal cage while a Whimshurst machine fired huge great sparks at him. He emerged unharmed.