Everyone wants to increase the speed of their internet and your problem is quite the opposite, that’s funny. But yes, there is a way to decrease the speed of your internet but that’s for some specific sites speedput
Like if you don’t want that your kids watch movies on Netflix at night, or if you don’t want that your kids don’t stream Youtube, you can limit the bandwidth for these websites. There is always an option in the settings of your router, that you can limit the internet for them or you can temporarily block these sites. You can get help from this site as well.