Suggestions to help me repair my 3TB HD?

From my experience, when an hdd starts failing, just shelve it asap and get a new one. I tried all different sorts of methods and, for me, they were at most very short temporary fixes. This is from experience with multiple bad and old hdds over the years. Just get a new one and enjoy the peace of mind that comes with knowing you'll get no stupid error when opening a game or a file.

I know it's not what you asked for, but it's just my two cents.

Try reseating the cables or using other ones, they may have become loose. If that doesn''t help get a new HDD and start copying your files. You basically can't repair a HDD or SSD.
Edit: If it's only Steam games then isn't so bad. Try copying the most important files & folders first as it could die any time.

Seconding what LittleBibo1 said, reseat the cables (if possible use new ones), and start to transfer the files from it to another one, although you could try to change the plates from your failing hdd to another one and see if it solves the problem, you're more likely to just ruin both of them.
Sometimes I get hardrives with "head crashes", but even when I can bring them back, if they start to behave like this, I just shelve them.

In my experience, HD's that start giving errors like that eventually get worse & worse (like within a few months) until suddenly one day they stop working completely. Like others said above, I recommend copying all precious files off of the failing HD right away (e.g. game saves that aren't uploaded to Steam Cloud). Good luck trying to fix the HD - at least you won't lose anything after copying your files off even if the HD dies!

If you don´t care about the data so much as you do the disk you could try HDD LLF Low Level Format Tool (free for personal/home use, just Google it), it helped me with a failind hard drive once.

Agree with the others, quickly copy your important files to another HDD if possible. Errors like that could be an early sign that your HDD will get broken. Even if there is a workaround to make it working fine for some time, it will be back to error at some point and get worse very quickly.

Other people have already commented on simple repairs.

Make sure that no bad sectors are recorded.
When a bad sector is identified, there is a high probability that a hardware defect has occurred.
This is not yet the case with SSDs, but if it is a hard disk, the result is near fatal.
https://crystalmark.info/en/software/crystaldiskinfo/
If there are no records of bad sectors?
Perhaps the data is corrupted due to momentary power failure or software problems, so it may be safe to format and reuse.
(Might not be a good idea for an old hard disk with a long total usage time)

In any case, don't forget to back up your data daily.

You need to chkdsk, otherwise it won't significantly help.
Chkdsk could performed faster if you partition your HDD.
Other solution would be format your HDD then set a partition, or get a new HDD.
You can try every solution on the internet, but i can guarantee you it will waste hours of your time or maybe days/weeks.

Well, there is two types of errors on HDD - software and hardware. If that's software errors (like, corrupted filesystesm) - it can be fixed with almost any filesystem checker, like mentioned chkdsk. Hardaware errors tho almost never can be fixed, sadly, so if it's hardware - you need to get a new drive ASAP. Only few things that can cause hardware errors but can be fixed:

• bad (or oxidized) data cable. replace it to check this possibility.
• bad PSU (it can be because of old age, even if you have a quality PSU). This can cause all kinds of strange error, not only on HDD. Fix is to either replace PSU, or reapair it first (usually involves changes all capacitors in PSU to a new ones).
• oxidized connectors on HDD pcb. You can easily find a video tutorial how to clean those, here is one for example: https://www.youtube.com/watch?v=lNMW5f6MZo0

Sadly, from my experience, issues above are extremely rare, and actually dying HDD is much more often. So, if you can allow it - I would recommend to not waste time and just get a new HDD. If you're short on money (or have a lot of spare time and feel adventurous) - you can start with checking the above list.

I wanna thank you all for the replies. You guys helped a lot.

Decided to run chkdsk one more time and got this:
Erro de discoc0000483
O disco não tem espaço suficiente para substituir clusters inválidos
detectados no arquivo 45 de nome \Steam\steamapps\common\Ancestors The Humankind Odyssey\Engine\Binaries\ThirdParty\PhysX3\Win64\VS2015\PhysX3Cooking_x64.dll.

Disk has not enough free space to replace invalid clusters.
It happens with many files...

Manufactor of the HDD?
If it is a SSD, then there is no chance to repair.
If it is a HDD you can try to repair it, most manufactors supports to connect the HDD via "USB-TTL RS232" Rx/Tx.
With a terminal program (Hyperternial.exe from XP can do this job) you can then connect to the internal diagnostig of the HDD bios.
First you have to delete the SMART Data History and then you can do internal test and diskformat, on some types also a LowLevel format is supportet.
But it is extremly hard to find informations how to connect, what settings you need for serial port and how you enter and use the internal diagnostic.
For Seagate you have the best chance to find all this informations in the web, there are also exist some HDD (Pay)applications with documentation and gui to do this HDD Bios "games".
But with a chance of 95% there is no chance to fix your drive, but if you have RS232... It's worth a try and you can learn something from it.
Most dead HDD's i tried to repair, are killed by overheating.
I had already installed fans for the hard drives than for CPU's not even heat sinks have been installed.
I fixed one of my seagates with this method (recover Current Pending Sector Count), after 49k hours i reset the smart history, format the disk, hours of internal test (dont forget the Fan) the disk is working fine again, ok the temperature sensor is not working and i use the disk only as a backup of the backup of my backup.
Try to find information and help in "forum hddguru", also you can use https://www.smartmontools.org/ for detailed SMART informations of your Disk.
Good Luck 🍀

Any recommended SSD brands? I tried sandisk before and regret that.

Premised that i don't think is good for you to do,but i want to share one my personal experience,
Sometimes when my hdds stop to work i'm habit to remove the sata cables and trow some airs at the insides of it,this remove dust and hdd back to work perfect
also
3 years ago my ssd hdd stop to work (full death) then i open it put some flux in the nand memories and trow some hot airs on it after that i wait 1 hour without move it and i close it and retry use it and it will work until now (is the ssd i use now main hdd and never had 1 problem since that)

i think these don't help for you but for me has work different times in some cases.