I have a 1T silicone power hard drive that had two fat partitions , the first one was around 800GB with photos and videos that are very valuable.
I accidently used the dd command and wrote fedora iso to the beggining of the drive. i did "dd if=fedora.iso of=/dev/sdc" , I actually ment to write it to /dev/sdd.
so now the partition table is deleted and probably some of the photos.
what will be my best way to recover the data ?

Thank you

You can recover your data from free space.. mean where overwrite ends if you overwrite 100 gb the rest of 700 gb recoverable with any data recovery software or contact any nearest data recovery engineer.

Overwrite data is impossible to recover the technology all i know is 0 and 1

Read and Write

there will be no way to recover previous data is you write new data into sectors.

According to the description your drive is OK, so all you need is logical recovery.
Scan the drive with a data recovery software like UFS Explorer (and you will not need a pro-level edition).
Free alternatives exist as well, but I can't tell anything about the quality of results they provide.

Overwritten part is lost forever.
Be sure to recover the data onto another drive.

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