Duplicate wordpress site and import to new folder without crashing servers

I have a wordpress site and i have created new folders but i would like to use the files and plugins on the main site in the new folders.
But i have tried tons of plugins and they have all crashed the server and made all of my sites very slow.

Is the anyway that’s proven to work without crashing the servers ??
Because i don’t want to crash thousands of websites again !!!!!!!!!!!!

Can you extract files from the control panel and then import them to the new folders ??

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