The receipt doesn't prove who you voted for, just that the associated vote was counted.
>every person is able to fully understand what is happening. Additionally you do not need to have a strong trust in the implementation of the cryptography
Are you sure you fully understand what is happening with paper based systems? You don't know which people looked at your vote, who they reported to, how the votes were summed up locally, how the information was transmitted to be centralized, who handled this info and how they made their decisions etc. It's actually much easier to understand and trust an open-source computer system than the mesh of social institutions, obscure regulations and personal idiosyncrasies that make the paper systems run. And you do trust your entire wealth to cryptography each time you make an online purchase, you know.
>For a large scale attack on computer based voting, you would need to bribe way less people
No amount of bribes will break cryptography, and proof that the system worked correctly is easy to supply by opening up the machines and software for public inspection. By contrast, we'll never know what, for instance, half a dozen election officials may have discussed in a tiny room (Florida 2000, Iowa 2012) and how they arrived at their decisions.