is adobe flash player safe to download

Only if you manually download it from get.adobe.com, helpx.adobe.com, or the Flash Player pane of System Preferences, and keep it up to date.

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And be sure to read How to use Internet plug-ins in Safari for Mac - Apple Support

Only if downloaded from https://get.adobe.com/flashplayer/

Only from adobe.com. There are many places offering flash player installers in pop-ups and they likely contain malware.