iMac is suddenly really slow

Hi,

Lately (for the last week maybe) my 6-year-old iMac has been running pretty slow, which it wasn't doing before (it's an old model, for sure, but it was running pretty well, and now all of a sudden it stops, shows the colored ball, and takes a lot of time to open).

The only two things that I can think might've affected the performance are:

1. Recently I tried to install a program and without realizing I opened one of those fake "installers" and said yes to installing some other program I wasn't intending to download, however, I closed the installer as soon as I realized and have now run Malwarebytes, which detected no problem in my Mac.

2. I recently moved to a big city, and took the iMac in my car in its original box. I worry it might've suffered a hit or something which could've hurt the hardware, who knows.

Anyway, this is my EtreCheck report (the only problems I can see are orphan files and then one of the unsigned files, which says is possibly adware, but from the name seems to be the updater for the MEGAsync app, which I've been using without issue for some time now, however, the install date is from TODAY, which makes even less sense because my mac has been running really slowly for about a week now):

EtreCheck version: 4.3.6 (4D041)

Report generated: 2018-09-09 15:26:40

Download EtreCheck from https://etrecheck.com

Runtime: 5:12

Performance: Below Average

Problem: Computer is too slow

Major Issues:

Anything that appears on this list needs immediate attention.

No Time Machine backup - Time Machine backup not found.

Unsigned files - There are unsigned software installed that could be adware and should be reviewed.

Minor Issues:

These issues do not need immediate attention but they may indicate future problems.

Clean up - There are orphan files that could be removed.

Low performance - EtreCheck report took over 5 minutes to run. This is unusual.

32-bit Apps - This machine has 32-bits apps that may have problems in the future.

Abnormal shutdown - Your machine shut down abnormally.

Hardware Information:

iMac (21.5-inch, Late 2012)

iMac Model: iMac13,1

1 2,7 GHz Intel Core i5 (i5-3335S) CPU: 4-core

8 GB RAM - Upgradeable

BANK 0/DIMM0 - 4 GB DDR3 1600 ok

BANK 1/DIMM0 - 4 GB DDR3 1600 ok

Video Information:

NVIDIA GeForce GT 640M - VRAM: 512 MB

iMac 1920 x 1080

Drives:

disk0 - APPLE HDD HTS541010A9E662 1.00 TB (Mechanical)

Internal SATA 3 Gigabit Serial ATA

disk0s1 - EFI (MS-DOS FAT32) [EFI] 210 MB

disk0s2 - Macintosh HD (Journaled HFS+) 999.35 GB

disk0s3 - Recovery HD [Recovery] 650 MB

Mounted Volumes:

disk0s2 - Macintosh HD 999.35 GB (455.92 GB free)

Journaled HFS+

Mount point: /

Network:

Interface en0: Ethernet

Interface en5: iPhone

Interface en1: Wi-Fi

802.11 a/b/g/n

One IPv4 address

Interface en4: Bluetooth PAN

Interface bridge0: Thunderbolt Bridge

System Software:

macOS High Sierra 10.13.3 (17D47)

Time since boot: Less than an hour

System Load: 2.11 (1 min ago) 1.73 (5 min ago) 1.23 (15 min ago)

Security:

Unsigned Files:

Launchd: ~/Library/LaunchAgents/com.valvesoftware.steamclean.plist

Executable: ~/Library/Application Support/Steam/SteamApps/steamclean Public

Details: Exact match found in the whitelist - probably OK

Launchd: /Library/LaunchDaemons/PT.updd.plist

Executable: /Library/PrivilegedHelperTools/PT.updd

Details: Exact match found in the whitelist - probably OK

Launchd: ~/Library/LaunchAgents/mega.mac.megaupdater.plist

Executable: /Applications/MEGAsync.app/Contents/MacOS/MEGAupdater

Details: Domain name invalid - possibly adware

32-bit Applications:

10 32-bit apps

Kernel Extensions:

/System/Library/Extensions

[Loaded] SteamInputX.kext (4310.02.31 - SDK 10.8)

System Launch Agents:

System Launch Daemons:

Launch Agents:

Launch Daemons:

User Launch Agents:

User Login Items:

MEGAsync Application (? - installed 2018-08-15)

(/Applications/MEGAsync.app)

iTunesHelper Application (Apple - installed 2018-02-18)

(/Applications/iTunes.app/Contents/MacOS/iTunesHelper.app)

Internet Plug-ins:

AdobePDFViewerNPAPI: (installed 2018-08-17)

QuickTime Plugin: (installed 2018-02-18)

AdobePDFViewer: (installed 2018-08-17)

PepperFlashPlayer: (installed 2018-08-14)

3rd Party Preference Panes:

Flash Player (installed 2018-07-28)

Time Machine:

Time Machine Not Configured!

Top Processes by CPU:

Top Processes by Memory:

Top Processes by Network Use:

Top Processes by Energy Use:

Virtual Memory Information:

Software Installs (past 30 days):

Clean up:

~/Library/LaunchAgents/com.movavi.converteragent.startup.plist

'/Applications/Movavi Video Converter 8 Premium.app/Contents/MacOS/ConverterAgent.app'

Executable not found

~/Library/LaunchAgents/launchkeep.cold-turkey.plist

/Applications/Cold Turkey Blocker.app/Contents/MacOS/Cold Turkey Blocker

Executable not found

Diagnostics Information (past 7 days):

2018-09-09 15:17:58 Google Chrome.app Hang

/Applications/Google Chrome.app

2018-09-09 15:01:28 Last Shutdown Cause: 0 - Power loss

2018-09-09 12:34:29 logd Crash (2 times)

/usr/libexec/logd

End of report