Well you purchased an entry level iMac that was designed for not much more the basic e-mail and simple web surfing however you installed professional grade apps on it.
There are many things wrong, first and foremost you do not seem to have ANY backup for the computer which is a 100% guarantee that you will permanently lose data. At the very least you should be using Time Machine ( Back up your Mac with Time Machine ) that is the first thing you should address!!!!!!!!!!!!!!!!!!!!!!!
The primary bottleneck on your machine is the glacially slow 5400 RPM HD that is installed, this is a performance killer. It is also 5+. years old and may be showing signs of age. After you have done a Time Machine backup, please download DriveDX and test the HD! If any errors appear that indicates the HD is damaged and should be replaced or replace the whole machine. If you want to keep the machine then purchase an external SSD (I'd recommend the OWC Envoy Pro SX ) and external SSD as your startup drive. Instructions for doing this are pretty simple if you can follow directions, the directions are in How to setup an external SSD as your startup disk.
If you decide to upgrade to a newer machine, I would recommend getting a Mac mini and an external display. A well equipped system will cost <$1500 USD including a high quality display. You can use the iMacs keyboard and mouse.
