Plugin imported duplicate orders & Trying import same products

Hi Guys

recently, the plugin has following issues:
1. imported same orders multiple time, how can i remove the duplicate orders.
2. trying to import same products multiple times, so the import speed is extremly low.
3. when the import start, the site is almost stuck, log file return 500 or 503 as well, how can we solve this issue?

pls check the screenshot and log file.