To fix the slow internet issue kindly follow the given steps:
1. If you are in weak signal areas, change your location and try again. Remove your phone case if there is one, for a metal case will block the reception of the signal.
2. Check with your operator to make sure you have shopped data plans, and there is still unused data in your SIM card.
3. Reinsert your SIM card or try another SIM card on your phone.
4. Check phone settings:
Make sure Airplane mode and WiFi are turned off and enable the mobile data.
If there is a VPN connection, disconnect it.
Adjust the preferred network type to [4G/3G/2G (Auto)].
Change or reset carrier network settings.
5. Restart your phone and see if you fixed the issue.
6. Detect and update ColorOS version
7. Back up and transfer the data on your phone first, then reset your phone to its initial state and settings.
8. Multiple Apps running in the background will consume network speed , so close the APPs when not in use timely. For example, downloading files in the background while watching videos online might affect the buffering speed of the videos.