Macbook Pro is Excruciatingly Slow [duplicate]

Question

I have a Mid 2012 Model Macbook Pro, nearly 3 years old, and my computer has recently become extremely, stupidly slow. It's becoming hard to perform simple tasks on the computer, like opening a Google Chrome Page, opening any app on my computer or even switching to a different application via the dock. I use this computer for school, however much of my classmates (who have the same model computer) aren't having the same problem as I am.

Usually, it takes about half an hour for my computer to start up and log in, and another half an hour to get everything set up on my desktop (as in loading up desktop, dock, menu bar and letting the computer speed up and stabilise). Below is an image of my Activity Monitor:

I have nothing on my desktop as of now. My Downloads folder is rather full, and I still have 200 GB of storage out of my 500GB remaining. I can't figure as to why it is this slow, and I know it's not because of my internet connection because I have a second Macbook Air laptop (relatively new) that runs at beautiful speeds.

What should I do about this?

Specifications:
Macbook Pro (13 Inch, Mid 2012)
Processor: 2.5 GHz Intel Core i5
Memory: 4 GB 1600 MHz DDR3
Graphics: Intel HD Graphics 4000 1536 MB
Storage: 500GB total, 200GB remaining

Answer 1

Troubleshooting is a process of elimination, so you will need to try a number of things one by one and take note of the results.

Start in Safe Mode

First of all, try starting your MacBook pro in Safe Mode and testing to see whether you still suffer the same sluggishness in performing typical tasks. To do this, follow these steps:

1. Shutdown your MacBook Pro
2. Restart your MacBook Pro
3. Immediately press and hold the Shift key.
4. Let go of the shift key when you see the login window.

Use the computer as per usual and determine if it's working faster now? Report back.

Run hardware diagnostics

You should also run some hardware diagnostics. To do this, follow these steps:

1. Shut down your MacBook Pro
2. Restart your MacBook Pro
3. Press and hold the D key before the gray startup screen appears.
4. After a while, Apple Hardware Test (AHT) will start.
5. When prompted, select your language and click the right arrow.
6. When the AHT console appears, you can choose to run Basic tests by clicking the Test button. I suggest you select the "Perform extended testing" checkbox before you click the Test button.
7. Your test results will appear in the window in the bottom-right of the console.

Note that the extended test will take some time. Take a note of the results and report back.

For good measure, it may be worth resetting both your NVRAM and the SMC.

Reset your PRAM/NVRAM

Reset your Non-Volatile Random-Access Memory (NVRAM) by following these steps:

1. Shut down your machine. Yes, a full shut down, not just logging out.
2. Press the power button and then press the commandoptionpr keys. You have to make sure you press these keys before the gray screen appears or it won’t work.
3. Hold those keys down until your Mac reboots again and you here the startup chime.
4. Let go of the keys and let your Mac reboot normally.

Note: When you log back in you may need to readjust some of your system preferences (e.g. mouse speed, time and date/timezone, etc).

Reset the SMC

For your model MacBook Pro, resetting the System Management Controller requires these steps:

1. Shut down your MacBook Pro
2. Keep the MagSafe adapter (power cable) plugged in.
3. Press at the same time shiftoptioncontrol (on the left side of the keyboard) and the power button
4. Let go
5. Turn your computer back on with the power button.

Once you've done all these steps let us know how you went.

Answer 2

First of all get rid of Avast, it's at least useless. Furthermore it modifies low level functions of the macOS, what can cause dangerous consequences.

Test.