Resizing partition impossible

I have a 512 Gb SSD in my Inspiron 13. I resized the C partition from 460 Gb tot 305 Gb. The free space was then changed into the D partition of 156 Gb. So far, so good.

Now i found that my D partition is getting full very fast and i want to make it bigger.

Therefore I try to resize my C partition to make it smaller but i can only take 66 Gb while i have 259 GB unused space.

I tried this with disk management in Windows, Aomei, Easeus, Minitool... Always the same problem.

How can i resize my C?

I see also that both C and D are bitlocker encrypted, which is very strange because i have Win10 Home edition. Does this have something to do with my problem?