I would like to enable bitlocker on my C: drive, but I dont understand the following message:

If it's the hardware, which part exactly? I have a recent asus motherboard with UEFI. How can I find out if my motherboard supports TPM?

These are your motherboard’s specs. It doesn’t mention a TPM at all. That means your motherboard doesn’t have a TPM and you cannot install one.
These are the specs of a motherboard featuring a built-in TPM. Note how the TPM is prominently advertised. Because this technology is largely irrelevant to consumers, there are only five Socket 1150 motherboards that have it.
There is yet another category of motherboards, with this one being an example. They have a connector where you can install a TPM module. These modules are available starting from about $10.