Accidentally clicked the wrong save to sync and I don’t know how to get my other save back

From the sound of it, you have accidentally saved over your old save. This usually happens when you accidentally choose the wrong save to sync. There is nothing you can do to get it back, and will have to start the game from the beginning.

I accidentally clicked "Sync last saved data" and lost several days of gameplay

Neither of the options worked for 7 days to die. Fortunately my progress for my other games seemed to have come back, I think its because my old Laptop didnt get the chance to sync my save for the specific game, I mightve quit it accidentally or something along the lines of that. I appreciate the help though.

i didn't "accidentally" did it, it was the only option that worked. I kept clicking the "try again" thing but didn't work so I had to click the "sync last saved data" and ended up loosing everything (twice).

That's hell of a lot of problems.

With the saves. Are you always connected to Live?

Saves are automatically synced to the cloud and only cached on the hard drive. If you play while offline a lot then saves might not get synced. This can also cause problems if your system clock is wrong as saves may have the wrong date stamped on them and
get erased next time your console is online and synced. Whenever you disconnect the power the system clock is reset to something like 2013. If you don't connect to live the clock will stay wrong and cause problems.

But due to the other problems there may be something else wrong.

You could try doing a factory reset?

If factory reset doesn't fix it and your console is still under warranty then it might be worth taking it back to the shop to be replaced.