Macbook pro 2014 is really slow

Uninstall BitDefender by following the developer's instructions. Anti-virus apps, cleaning/optimizer apps, and third party security software are not needed on a Mac and usually causes more problems than they solve because they interfere with the normal operation of macOS.

Also, VPN software does not provide the security you think it does. The only time a VPN provides security is when you are connecting to an employer's or business' VPN server to access that network directly. Otherwise a VPN is only useful for bypassing local network restrictions.

You may want to review this excellent article written by a respected forum contributor:

Effective defenses against malware and other threats - Apple Community

Please run DriveDx and post the complete text report here using the "Additional Text" icon which looks like a piece of paper. I want to check that third party SSD you have installed.

Enable TRIM support for the SSD to see if that makes any difference. You need to enter the following command in the Terminal app:

sudo  trimforce  enable

You will be prompted for your admin password. Nothing will show on the screen while typing the password, you will need to press the "Return" key to submit the password.

After enabling TRIM, boot into Recovery Mode (Command + R) and run Disk Utility First Aid on the APFS volume which I believe will help to immediately trigger a TRIM event so that you may find out more quickly if enabling TRIM has any effect, otherwise it is hard to say when macOS will trigger a TRIM event on its own.

I don't see anything else wrong with the DriveDx report for the Transcend SSD, but half of the health attributes are not known so it is really hard to evaluate the health of the SSD.

Those VPN apps you have installed (TunnelBear & SurfShark) don't provide you with the security you think it does....they are only useful for bypassing local network restrictions. The only secure VPN is one which is used to connect directly to your employer's VPN server to access a work/business network, or to your own home VPN server (most people don't have a home VPN server). I would recommend uninstalling both of them by following the developers' instructions.

You have some third party software I'm not familiar, so I will need to let another more knowledge contributor assess the other third party software which is automatically launching at boot & login since I'm not a macOS software expert.

You are using a very outdated version of EtreCheck, please download & use the most recent version which is v6.8.x IIRC. The EtreCheck report is missing critical information which may provide more clues. Also make sure to use the "Share" button within EtreCheck and select "Copy Report" so a properly formatted report gets transferred to the Clipboard so it is properly formatted when you paste the contents of the Clipboard into the "Additional Text" field on the forum. Or maybe the outdated version of the app is why the formatting of the report is off.