Verify what’s happening (charge voltage/current) using an app like GSAM Battery Monitor or Accubattery. Accubattery can also perform a battery health assessment by monitoring the min/max voltage of the battery after 2 or 3 full charge cycles (it tells you how to do this).
It may be that you have a low power charger, or a cable that limits charge current, a faulty charger, or an app that’s eating power.
If it charges slowly, but you have good voltage/current, there may be something running that’s consuming battery. Both GSAM and Accubattery will show app battery consumption.
For the network performance issue, resetting is the most definitive approach. Then you’d eliminate software causing issues. Alternatively using a firewall app like NoRoot Firewall, you can bIock network access for most apps and see if performance improves.
But network is a complex question - is it your connection, is it something between you and the servers, etc.