How can we compress the PST size without losing any original data?

I have a very large size of PST file, so now I want to improve my Outlook performance. If you have any ideas which help I can easily compress the large size of PST file, then share your informative idea here.

Not really a PowerShell question and the short answer is that you don’t really need to compress the file manually.
Outlook will automatically compact the file if it (Outlook) is open and the computer is idle.

You can run a manual compact by double clicking the file in the Data Files section under Account Options.