I've bought this phone mainly due to it's future camera capabilities (promised 4k with Denim), with Windows Cyan I was very disappointed with the low light video recording ability, even with Denim it's worse than with my Lumia 920 it has poorer camera! The screen and the recorded video is flickering and becoming purple-ish!
That's a generic problem of the 930. The three 930's I've already have all had the same problem (I'm waiting on the new unit as I had to had it replaced...again!).
On last Saturday (24.01.2015) I was trying to record a ~20 minute video from a tripod stand (good ventillation all around) about our salsa dancing performance, but the phone failed to do it, my Nokia Lumia 930 overheated during 4k recording!
That is normal. ALL phones that record on 4K overheat after a while because 4K demands a lot from the processor and remember:
smartphones don't have fans to cool down the system.
I don't know how Microsoft implemented 4K on the 930 (as mine was sent to replacement before I got Denim), but my Z3Compact from Sony actually gives a warning when it starts to heat up and then shuts down before the phone starts to overheat.
There's really nothing you can do about it. The best you can do is, next time, record thing in 1080p. Unless you have a 4K TV, there's little point in shooting with 4K anyway.
Moreover: The upper left-side of the screen came off ~2mm from the plane of the metal, I've read on forums that it is due to poor quality screen fixing glue; it can cause not only visual issue but the proximity sensor to fail, by this e.g. not able to end a phonecall!
The battery drains very fast and the back side of the phone is too hot to hold it while using it!
The 930 I've left for replacement was sent precisely because of the lifting of the screen. You have to get it replaced.
And yes, the 930's battery s*cks big time. And that's because the phone has a miserable 2400mAh battery to support a 5" 1080p screen. It's simply not enough (My Z3C has a 2600mAh battery for a 4.7" 720p screen...result: I have 2 days of battery life on the phone. The 930 doesn't last me 24 hours).
I've read in a forum that even though my phone is not originated from a mobile shop (so it doesn't have a stamp on the warranty card) I can take it to the nearest Nokia Care point. (120 km from my home town...) Is it true? Do i need to write an e-mail about it to a central e-mail or so? What's the e-mail address?
As long as you have proof of purchase, you can take it to a Care Centre. Some Care Centres, however, require that the IMEI of the phone is written on the proof of purchase. However, since Microsoft's website shows you the phone is within the warranty, I suggest you also print that page, just as a precaution and take it with you.
Normally you have to take the phone to the Care Centre yourself.
But given the distance between you and it, I'd suggest you contact Microsoft's support in your country to see what can be done. I'm not sure how Microsoft will implement the Care for their phones, but the Surface Care has a service that picks up the hardware from you at your home address. Maybe they can sort it so that you can also have your phone collected.