At 1000 Eur you should have a bike that would be able to take pretty much all street riding you can throw at it - assuming you don't ride down stairs, into bollards, big potholes and curbs. You probably have a right to feel annoyed.

It's not entirely clear what you mean by a spoke "ripped halfway out". Ripped, I think of spoke nipples pulling through the rim, which isn't really repairable in a reputable way - unless it's the nipple head that's popped off, or the flange that has sheared.

Spokes coming undone is usually a sign of improper assembly and/or insufficient tension. Either the spoke was too loose to start with, or you had residual spoke wind up which caused it to work itself loose once you started riding.
On a new bike, the wheel might still be salvageable - if it's worked through properly. This means checking for tension and making sure there's no residual wind-up throughout the wheel.
In marginal applications, which yours shouldn't be unless you're a really chunky lad, thread lock may be called for.

Here too there's some detail missing "They told me they had to replace the chain and the gear and also clean the hub for 125 Euro,".
Chain, that's clear enough, but heck, I can get a perfectly serviceable SS/IGH chain for 5 EUR. A stainless one for 14 EUR.
Gear, that's a bit vague, I'm guessing you refer to the sprocket - the toothed wheel the chain runs over. Should be about 10 EUR - but I can't imagine one being rusted so badly that it'd have to be replaced b/c of that.

It wouldn't be my 1st guess, but I assume it's possible that you had accelerated wear/elongation of the chain, for unknown reasons, which then caused the sprocket to wear down prematurely. Or your sprocket was made of that infamous cheese alloy, which pops up every now and then.

Either way, if you subtract the likely parts cost, you're left with a hefty sum that's supposedly has gone to cover working time.
It'd be interesting to know how long they've claimed to work on the bike.
125 EUR would almost cover the cost for a replacement set of all the hub internals. What's left from the parts costs should certainly cover a detailed tear down, clean & relube.

Or maybe they changed the chainring/crank too? That'd help explain things.

Then there's this bit:"clean the hub". Last hard data I read myself recommended an IGH to be flushed/lubed first after 6 months of regular use, then yearly. But I know plenty of people/bikes who have blissfully ignored this advice w/o any visible negative effects.
Either way, modern hubs are such sealed units that flushing/lubing really is a shop job rather that something the rider can do with the wheel on the bike.

I wouldn't expect to have to do any early maintenance on an IGH unless the bike had been dunked in water deep enough to submerge the hub.

So we come to:"it was my fault for not oiling it and that's why it was rusted", and I have to agree with them there. Maybe the factory lube on your chain was a bit on the light side, maybe it got washed off in the first rains, maybe some bored sales attendant wiped most of it off - which made the chain rust faster and harder than normal. It's easy enough to check, and it's easy enough to do, so it falls on the rider.

And "A friend told me that it is a fragile bike because it is a luxury bike." - I don't agree with that. At 1000 EUR it should be a solid workhorse of a commuter bike, no particular pampering needed.

But while IGH set ups are usually held to be more weather resistant, they are less forgiving when it comes to torque, and adjustment issues. Many of them comes with tooth count limits, ie, " if your sprocket is this number, your chainring should be that number".
If you've made a life long habit of mashing, maybe, just maybe, you're strong enough to do damage to an IGh even if you're inside the tooth count recommendations.
And putting the power down before a gear has fully engaged, well that'a surefire recipe for trouble for any drive train. It can strip teeth of sprockets, chip pawls and serrations in freewhee/freehub clutches and trash cogs in IGHs.

So I guess it's a mixed judgement. You shouldn't have the spoke trouble, you have failed in caring for the chain, the cost for the work seems a bit steep and the original reason for the chain skip/slip can't be settled from afar.
At the price, and some sort of average rider, I wouldn't have expected that kind of trouble - apart from the chain rusting.