Sorry there are on upgrade possibility with this system. Here’s a similar systems specs: [https://www.consumerreports.org/products/chromebooks/asus-chromebook-c300sa-ds02-lb-387263/overview/|Asus Chromebook C300SA-DS02-LB]
You are more like hitting a WiFi network issue. Unlike many standard PC your’s leverages the Internet for storage. So if you have something local the speed would be fast, but if you are reaching across the Internet the connection to it will slow down when started and shutdown as it needs to open as well as close files remotely.