Your assumption is correct, my input tensor consists of float values, so this explains to me why it is not working properly.
The F.binary_cross_entropy() function produces very high losses, so I tried with F.mse_loss() instead, which produced better loss values but I assumed that this is not correct, since the MSE loss is not mentioned in the Kingma paper (https://arxiv.org/pdf/1312.6114.pdf 26, see section 3 loss function).
So overall I`m not sure which loss function would suit my case best. I am open to any suggestions at this point.
Maybe there other things, that are likely to be the source of high losses, but I still have to find them.
Thanks for your reply