Hi @Grego, if you follow the below steps, you'll be able to change this setting.
1. Open a browser ( chrome ) and in the URL address box type in - 192.168.8.1
2. Log-in details are - Username: admin and the same for the password ( unless you ever changed them in the past )
3. When you're logged in click settings on the top of the screen
4. Go to 'WLAN Basic settings' and you'll find the 2.4ghz and 5ghz options in here
5. If you're connected to 5 gigahertz can you choose 2.4 or if connected to 2.4 choose 5. When you've this selected can you see if you notice an improvement?
50mbps is a very good speed to be getting on the router 😊 Mobile data speeds and wifi speeds can differ. For example, your router speed can be affected by external factors (walls/distance from the router etc) whereas this won't affect mobile data as much as its only the one device you're using. Hope this helps!