To Agung,
For the demo account, it is intended to get to know / learn trading. Lagging can occur because it cannot fully access the running price or other tools.
Regarding the server IP, it actually doesn't affect anything. Because it is set by default by the broker specifically for demo accounts. As for real accounts, when you open a real account you can choose the nearest server, or the broker will automatically provide a server that they think is close to the Indonesian region.
Thank you.