A common reason why your device is not charging as fast or as completely as before is that there is an issue with the charging cable. To remedy this, try inspecting where the cable plugs into the laptop. Use canned air to clean both the cable and where it plugs into the device. If charging problems persist, replace the cable as it is likely broken. If you still can’t charge your device effectively, follow this guide to replace your battery as it is likely dead or damaged.
The most likely reason for your laptop to shut down mid-use is that the cooling fan has built up debris in it, causing it to be unable to cool the device. This makes your laptop overheat and turn off. I would recommend using canned air to blow out the vents leading to the fan. These are located on the side and bottom of the laptop. If the issues persists, you can open the device up and check to see if there is debris build up in the fan or if it requires replacement. To get to the fan to clean or replace it, follow the instructions in this guide.