@Liverpool20 

There is parental menu but so far it looks like I can input only keywords and not websites. It looks like this: 

There is also security menu, which is where some of the tutorials block the sites, but I do not have the same menu there (they went through Access control - Host, I do not have that): 

Thank you for the quick reply :). 

  @Drakie 

Your router's Parental Controls and Access Control look pretty similar to that of the TP-Link C8 V4, for which you can find a detailed Users Guide PDF document here:

https://www.tp-link.com/de/support/download/archer-c8/v4/

Chapter 8 explains it in detail. How good it will work is another thing, though.

  @woozle 

Hello, thank you very much for your help. It seems the keywords should be used also for websites. It has finally occured to me to just try the site directly to see if it works and it does :). So thank you! I finally figured out that the ads are not from my tv but from google and that is why it is not working as I want. Sorry about that, I am not that tech savvy :). Thanks!