What's the difference between this bike:

Radon TCS Rohloff | Trekking Bike Shop

and this one:

Radon TCS 5.0 | Trekking Bike Shop

??

Did you read the specs? I know based on your recent posts you seem hung up on not believing their is a quality difference in bikes and components but the differences are apparent if you look at the specs. A big one is one bike has an integrated rear hub while the other has a more conventional gearing setup.

That's a difference.
what will that difference affect my riding performance/comfort/experience.......?

The main difference is that the more expensive model has the Rohloff internal hub, which by itself runs $1200-1700 depending on which version you get.

The main similarity is that neither of those bikes would last 3 hours locked up on a college campus, both would be thief magnets.

The Rohloff hub is a marvel of modern German engineering, by the way. Those who can afford them love them.

then how can i protect my bike ?! ok, i will get the TCS 5.0 , but even that one will be a magnet ?! o.O which one isn't a magnet !?!!

For a bike that will be locked up on a college campus, I would favor getting a quality used bike.

A steel late 90's mountain bike would be my personal choice, a Trek 800 or 900 series.

They can be had used for under $500 easily and because they look (and actually are) really old, they should blend in to all the other shinier bikes on the racks at University.

NO lock can protect a bike from a professional thief, no matter what any salesperson tells you.

University campuses usually have bike shops that carry used bikes, I would go make the rounds because personal fit is very important for any bike that you want to keep for 12-14 years.

By the way, one of my commuters is a Cannondale from 1996, and it's still going strong. A good bike will easily outlive its owner if taken care of properly.

I will be in Germany, so no trek there i will take a look into ebay

Be sure to learn how to lock your bike properly. A lot of bikes get stolen simply because the owner did something dumb like lock the bike to a short pole, or use a cable without a U-lock.

Lock Strategy

https://priceonomics.com/bike-locks/

https://www.nationalbikeregistry.com/proplock.html

If you get a bike with quick-release anything (wheel, seat, etc.), do something about that too, because the thief can just quick-release the thing right off your bike even if you lock the frame properly. This article shows how to lock your saddle if it's a quick-release saddle:
How to lock your bike - Bicycle Coalition of Greater Philadelphia

Thank you but cant the theif just cut the lock cable ?

I don't know. I locked a $1,500 105 groupset cross bike to the campus bike racks every day for three years of undergrad and three years of grad school and it never got stolen. I may have just been lucky, but that was quite a streak of luck if so. I locked the front wheel and frame with a Kryptonite U-lock and the rear wheel, front wheel, and frame with a Kryptonite chain and only did so during class hours and in busy areas. It never spent the night on a rack, as I lived off campus; I'm sure it would have been taken if I left it out overnight several times.

It was also neon green, so maybe its conspicuousness deterred thieves?

Read the articles. They all say to use a U-lock as primary lock, use a cable for secondary locking.

Also read the part about making your bike look less desirable by using a crappy looking saddle, or putting stickers, or painting it in weird colors, etc.