And i tried to enter my serialnumber to get a download for the software/drivers(if neede!), but it says invalid serialnumber. I just bought this in a shop - what to do?
You say you "just bought this in a shop" but that you are "trying to get a download of the software". Is that correct? If so, is it because you have no CD/DVD drive in your laptop that you are attempting to download the installation files? If that is the case, I don't think that will work for the particular software you have bought.
Some Magix software offers a free, downloadable, trial and you can use the serial number of a purchased version to fully activate and register that trial version. Unfortunately, I think there is no trial version of Rescue Your Video Tapes.
When you say you see a message that the serial number you have is invalid I suspect this is because the standard way of registering a serial number and thus having it attached to your account is to enter it on the appropriate screen after the program is installed. In effect, the program itself registers your serial number; without the program itself seeking to connect to the registration server, your registration attempts will not succeed.
I suggest your easiest option is to purchase an external USB CD/DVD drive - they are usually pretty cheap - and use that to install your software.
As @CubeAce has mentioned, I have removed your personal information as you are in a public user to user forum, which is not safe to leave such information.