Windows 7: External USB (not) giving errors [after gpt to mbr conversion]

I have an External USB.
It was a GPT Disk.
I turned it to an mbr disk and created a NTFS Primary Partition and problems started.
Ok, it is there, then in the middle of the copy, it is not.
Or it is there, but the copy process gets stucked.
Sometimes format is possible , sometimes not.
Before this conversion from GPT to MBR; the drive was 90% full.
So, if I have a drive like this having problems with;
how can make it work healthy again, that is if I can?
Do I write it with zeros? Do i format it with external software?
Do I format with from command prompt?
Do I format it to fat32 and ntfs?
What ways can return my drive to the healthy way of working before I converted it?
By the way, I checked and changed the plug and USB Cable and tried different ports.

When I connect the drive, I see the warning of "This drive can work faster if you connect it to a USB 3.0 port". I can see the drive in the "Safely Remove Drive Section" with its name,
But I can't see the drive in Windows Explorer or in Disk Management!
What the heck?
Thanks!

In linux, dmesg | tail result is

"Clean all" command (in diskpart.exe) should erase all information on USB.
Then create partition primary (for MBR disk).
You can format the new partition as NTFS or FAT32 (maybe format without the quick option)
I think FAT32 is the recommended format for USB flash drives as there are fewer write operations.

Oops! I guess I forgot to mention that this is not Flash.
It is a 2 TB External Desktop with its own power (with plug) I mean.

So,

select disc X
clean all
? (how do I create mbr disk or it is already there?)
create partition primary
format fs=ntfs

Last time, like twelve hours ago; I got stuck when I pressed 'clean'. I will try it again I guess and this time wait.
That is if it sees it!

Error!

After the error, it shows up in the disk management as not initialized, and when I try to initialize it; it says, the system cannot find the path specified.

I was able to initialize it and make a quick format after safely removing and connecting it again.
But I am sure that when I start to copy, it will give errors.
I will inform.

An empty disk is initialized when creating first partition.
If it is a primary or extended partition -> MBR
If you create a basic, system, MS reserved partition -> GPT

I am not 100% sure but on a GPT disk the first partition should be the "system" partition.

The clean command (without "all" option) is clearing all partition info so the disk should be decoded as uninitialized (data in areas outside partition tables is still on disk and can be viewed if you scan sector by sector)

I wrote around 50GB and it said, it is not located there anymore. I open the drive see the folder in there, but it shows empty, it shouldn't be like this. There is something wrong here, but what?

And it says 1.77 free out of 1.81 TB, but the folder seems empty.

Maybe chkdsk /r can fix this disk.

Where do I run it from?
C:\windows\system32 or K:\?
If I run it from C:\windows\system32, do I write chkdsk /r K:\?