Wifi Connectivity - Device Conflict / Inspiron 3585

Hi,

I purchased my Dell Inspiron about 2 months ago and it was working fine.

Last month it started having internet issues. It says I`m online and connected to WiFi but it will not let me access any websites/apps or programs.

I get the "hmmm, we cannot reach this page" or a TLS security warning

I`ve taken the laptop to work and my parents and the internet/wifi connectivity works fine on so I 'think' it`s not a problem with the laptop, rather a wifi setting, proxy setting or windows 10 issue (It will let me access Twitter but I`ve read that this has different functionality to 'normal' websites)

Two side notes to this;

At home if my laptop is on and connected to the wifi it blocks my TV, phone and other devices from connecting to the wifi - once I shut the laptop down all devices use the wifi with no issues.

Secondly, I can sometimes get the wifi to work on my laptop for 3 or 4 hours then it reverts to the connection issue again - but this is only after I`ve been to work and taken the laptop away from my wifi network and then returned.

I have an older laptop which is about 3 years old - that works fine on my wifi network with all other devices connecting as well with no issue.

I`ve done the usual rebooting routers etc. My internet provider has not been much help and claim it`s external/3rd interference - but that doesn`t stand up if my old laptop and other devices works fine on my wifi network

Please could anyone offer any suggestions or help? 

Thanks in anticipation.

Martin