Earlier quoted context omitted.
Deadly force can be lawful in Germany as well, reading Texas law I wonder which nuances of the laws make the biggest difference (assuming there's one). Could also be that the difference comes from owning land works differently in Germany (because it's much more densely populated) and of course owning anything except small guns is completely forbidden.
Only when threatened and self-defense has to be proportionate. If someone attacks you with a knife you would not be allowed to defend yourself with a firearm if you had one. This is very different from the law in Texas, where, from what I understand, if you catch someone in the night stealing you could just kill them even if they never threatend you.
Of course, if someone is simply stealing a Catalytic Converter you can't really shoot them, as it's a bit much... you can point a gun at them, and possibly even shoot the air, that's easier to argue as self-defence. If they threaten you back, the situation changes.
The problem is having a gun in the outside, in Germany, good luck with that... of course, if it's someone stealing something inside your house, it becomes a home invasion, which is a completely different thing than someone stealing your property on the street.
It's way more nuanced than Texas, which has a bit more clear cut law.