MAC slowness

Boot the Mac in the safe mode to see if the problem persist. For as far as I can see you have a Mac with an intel chip, so follow these instructions to boot in to the safe mode.

Start up your Intel-based Mac in safe mode

1. Turn on or restart your Mac, then immediately press and hold the Shift key until you see the login window.
2. Log in to your Mac.
3. You might be asked to log in again.
4. On either the first or second login window, you should see “Safe Boot” in the menu bar.

If the problem persists in the safe mode, it is caused by an external piece of software, then you should consider which software that you're running that can make your Mac slow

Unless you ordered your iMac with the optional Fusion (Apple's hybrid drive) or a factory-installed solid-state drive, a slow 21.5-inch iMac made between 2012 and 2019 is slow because of the under-spec hard drive Apple used.

Our 21.5-inch 2011 iMac with the entry-level drive for 2011 tests 30% FASTER than the entry-level drives used in 2012-2019 21.5" iMacs. Sad. Post back if interested in a cost-effective workaround.

⚠️ HOWEVER...

This: ...it will not open pics off of websites anymore

suggests you have other issues. Are you running any anti-virus apps? Any so-called "cleaning" apps? Client-side VPNs? Torrent software?

What browser is doing this? All, or just some or one? Have you installed browser extensions? Ad blockers?