Time Machine wont backup right, on Intenso 4TB

Hello,

i bought an external HDD (Intenso 4TB) from amazon a few weeks ago and since then, i always have to formate it again and again so it keeps "working". After a few days i always receive a message, that Time Machine could not create a backup on the HDD. I found no way of solving this without formatting the HDD and doing a new Backup.

This is the worst case solution for me, since i need those BackUps for me and my customers (Photos) and i just don't now what to do from here, any advice is greatly appreciated. Thank you so much.

(I texted Intenso Support, no answer in 3 days now)