Because you bought a base configured iMac it will never be fast unless you are willing to spend some money on it. It only has 8GB of RAM (the bare minimum to run Mac OS) and a glacially slow 5400 RPM HD. The RAM you cannot do anything about as those machines are not user serviceable. What you can do is to buy a USB 3.0 or 3.1 external SSD and then clone your internal HD to the SSD and use the SSD as your boot drive.
One thing I noticed in your report was there is adware installed, this will also slow down the computer. To get rid of it navigate www.malwarebytes.com and download the free version of malwarebytes and it should take care of the adware.