Question Dell Inspiron 7559 slow wired and wireless connection

Oct 6, 2019
I used to get the full 600Mb broadband that I have signed with my ISP but somewhen, not sure if last month or even more, it went down to 150Mb download speed and 180Mb upload speed (aprox) both wired and wireless conection (wired to the router directly).

I have been looking for a solution for days now, but nothing seems to work:

I updated EVERYTHING on my laptop including the network adapter, i uninstalled it and reinstalled again automatically and manually from realtek website, neither both worked (Current driver version: 10.36.701.2019).
Realtek property 'Speed & duplex' set to '1Gbps Full Duplex'.
Ethernet cable is working fine, I plug it into my partner laptops and it gets 550Mb.
Wireless tests on my smartphone goes up to 300Mb.
I have read about having problems with Smartbyte on Dell laptops but I dont have it installed.
I have disabled Avast Free Antivirus during the speed tests (using
I runned all the troubleshooting tools and the results are always the same, nothing wrong with my network adapter or anything else on my laptop.

Is there anything else that I can try before restoring my system? Please, help.