then i thought, lets try and erase the complete HDD ( 2 partitions ),create 1 partition + a downgrade to Snow Leopard and keep it clean for like a day or 2. didnt work either
Erase and install Snow Leopard again, but this time use Disk Utility to Erase with Security Option > Zero All Data on the hard drive instead of a the "quick format".
Your drive is suffering from bad sectors, this Zero will map plenty of them off, as long as you have plenty of spare sectors, if you run out the drive is worthless.
If your drive is failing, then it could be causing the bad sectors and it will have to be replaced.
If your moving the computer while it's on, the heads strike the platters and this can cause damage to the sectors.
So you have one last chance with the Zero operation, it might work perfectly fine after that or else it will need to be replaced and you can do that yourself on that model.