Repaired Windows 8.1 Core boots way slower and is not entirely Hungarian

Hi!

I've got a Dell Inspiron 15 3542-2521 with Windows 8.1 on it which was perfect until I had to repair it because it just crashed all the time. After a few trials (because my Windows was mostly Hungarian, except for a few things like repairing which was in German and was a great challange to find out what to do) I managed to enter my user and started a repair which promised to set back the windows to its original state while my documents remain.

So it happened, however I did not expect that my Windows would go back to German. I managed to download the Hungarian language pack but it does not work so well. I mean, before the repair, the Welcome title said Üdvözöljük and not Willkommen or the updates are also in German and you can find German phrases all over the Controll Panel and actually, everywhere. Any idea, how to make my Windows as Hungarian as it used to be? It is possible for sure because I have seen and used it and it was the same Windows.

Speaking of updates... First, I thought the boot is slow because it needs to update itself. But I had to realise that the boot is just way slower with or without updates. After the Windows' loading circle dissapears (which takes already about three times more than before), I used to log in my user immediately. Now I have to wait 5-10 seconds just to see the Welcome-screen (black screen in the meantime) and it remains there for another 10 seconds or more. I did not install back the programs I used before, so I have no idea what makes this process so much slower. Only the basic programs and drivers start at startup.