Before I try all that, is there any way to find my backup phrase via a different route than opening the Jaxx Depktop version? I mean, for some reason it won't open but there has to be a way around it to still get to my backup phrase?

If not, then can you please tell me if the menu "view" and then "Toggle Dev Tools" could be of any use?
Will I be able to access my private keys or backup phrase via there maybe?

And last but not least: would it hurt if I go to the official Jax website and download the newest version (even though it should have already downloaded the newest version automatically I would assume)? Will it still recognize my old wallet after this or am I completely locked out then and there is no way anymore to restore my wallet? I'm a little scared to try this option.