Thank you all for your answers and advice! Much appreciated!
@NoterMan I posted some extra photos. I don't know if it is as old as you say. If it is, then this could it be a valuable instrument? (I'm not planning on selling it, just curious. I bought it in a pawnshop for 10 euros (about 12 dollar)). The finishing isn't that clean and they used plywood on the lower parts.
The VSL is 49 cm which is about 19.29 inches.
@NoterMan and @Admin What kind of strings (gauges and type) would you use? I thought about ordering the thinnest electric guitarstring (0.09), but I am not quiet