I have a Dell XPS 13 9360, and it's been having several issues. When connected to the charger, the laptop becomes very slow. If I disconnect the charger, the laptop locks itself after 2-3 minutes and then shuts down completely showing locking. I'm very concerned about this.

How can I fix these problems?

Additionally, can anyone recommend the best charger for this model?

What is the required wattage for the charger for this laptop?