Try another website or service
One unavailable service does not prove the internet connection is down.
Try another device
If one device fails while another works, the device becomes the stronger suspect.
Try another network where appropriate
A phone that works on cellular but not home Wi-Fi suggests a different path than a phone failing everywhere.
Record the pattern
The pattern is more useful to support than a vague description of slowness.
General consumer technology information only. Interfaces and menu names change. Before resets, reinstalls, storage changes or other major actions, verify that important data is backed up and use current manufacturer/service-provider instructions.