zaman1111,
Sorry that you are seeing this issue.
1. Can you please update to version 10.1 from the Configuration Center ? Go to MyEclipse Configuration Center > Software > Software Available. Select 10.1, apply the changes and follow the wizard. Restart the IDE when it prompts to and switch to a new workspace.
2. Take a look at this link for performance issues :
https://www.genuitec.com/forums/topic/troubleshooting-memory-amp-performance-issues/
If you have already changed the heap to the suggested value and it has no effect then you could try increasing your heap beyond 768m and see if that improves the performance.
Also look at the second section for how you can change the JS settings to improve performance. I would suggest you move to the Basic mode.
3. You can also stop MyEclipse updating the maven index at startup. Go to the Maven4MyEclipse preferences page and deselect the “Download repository index updates on startup” option.
4. If you are still seeing the performance issues can you please elaborate where exactly you are seeing a slow down? Is it while working with specific editors or during startup?
Let us know how it works for you.