imac X OS 10.9.5 malware infestation help

Thank you for your response- I am challenged in this area and tired of feeling helpless, so I'm trying to learn how to take control.

The browser (Safari) is slow and gets stuck when loading pages, I get referred to other pages when I am searching. Worst of all, when I'm searching, I get interupted by a loud repeating alarm noise and a screen that tries to convince me I have an infestation. Often, I have to quit the browser to make the screen go away (I have never responded to these). Pop-up ads appear all over the place.

I changed my browser to Firefox and my search engine to duckduckgo today in the first step of an attempt to take control of my privacy. It looks like there is no upgrade available for Mac OS 10.9.5, unless I'm missing something, so I keep going in circles because everything seeems to want an OS of 10.1 at least. I thought originally I could upgrade to High Sierra, but apparently this is old information. Thought I would check and clean for malware first, but the issue of OS 10.9.5 seems to come up again.

Would the free 14 day version of Malwarebytes load and work on OS 10.9.5? Anyone with info regarding this is greatly appreciated! Thanks

Thanks for your help. It took a long time because I read it and I think I removed the 2 instances of adware and a couple of Kernel extensions. Limited RAM maybe because I have DAW (digital audio workstation- PreSonis Studio3) and a couple of peripherals- the apogee duet is one of them, soI undersatnd software w/those words. Silverlight was downloaded recently for Netflix viewing. Don't know what 'gatekeeper' software is. Hard to know what to do with all of this - don't understand launch daemons, but they don't sound good! If the report doesn't show, I'll try again.

Thanks for responding. I read this link- I already downloaded firefox today and switched search engine to duckduckgo, for starters. My imac is from 2013, and with OS 10.9.5, it looks like I could run Mojave, but the issue is the same as High Sierra- I need to make a backup on time machine, but the new OS doesn't work with time machine, and I'll be swithced to APFS instead of HFS+, so any backup is useless, right? This is troubling. Seems like I would be better off if I could upgrade to Yosemite or El Capitain, but where do you find downloads of these ? Can't even find High Sierra anymore at the App store. I would appreciate your advice (but I see you've been very busy- 92,617 posts for you and about 3 for me)

I ran etre Check again after I removed the malware/adware. This time I did not list a problem. This is the 2nd report. Thanks!