Without knowing exactly what happened it's hard to tell. Did you only change the partition table? In that case it's simple to re-create the partitions in the exact same places, and there's tools to look for them for you. Did you format a partition with a new filesystem? Then you're fucked. You can use photorec to scan the free space for files that might linger, but you're not getting the file structure back.

I overwrote it most with Linux, default install, shouldn't the original files be underneath
Ioth ext4

>>1552311
If you overwrote it with anything, the file structure is gone and unrecoverable with any automatic tool. Even if you study filesystems and look at the bytes manually, most of the important bits will be gone, so you'll be kept guessing as to what was originally there. You will still be able to scan for recognizeable file types using a tool like photorec, but it will output a lot of garbage that just happens to look like a file, and it won't be able to recover any structure, just file contents.