Create the updates directory in the website root on your server, make sure it is writable, and then try to update.

Thans for your reply. i did so. I still doesn't work. The download starts but then this message appears
fopen(/var/www/tmp/1466099471.zip) [function.fopen]: failed to open stream: No such file or directory

What do I do?

Try doing it manually following the instructions here -http://documentation.concrete5.org/developers/installation/upgradin...

I did so, but it stille doesn't work.
I have made an attachment of a screenshot whith the directory showing, that the map "updates" exist in the right place and the second screenshot showing that the files from the 5.7.4.2 is placed in the map.
When I try to upgrade, the same message as before shows

Please re-read the instructions as it appears you missed a step, also as you stated in your first original post you need to upgrade to 5.7.4.2 so you will need to download that archive and put it in the updates folder, not the most recent. Sorry, I should have mentioned that.

I,m sorry to have to ask once more. How do I download an older version? When I go to the sitehttps://www.concrete5.org/about/blog/core-releases/concrete5-5-7-4-2... and click "download", nothing happens.

Thank you so much. Now I succeeded in upgrading to 5742. I don't do anything more tonight (it's evening in Denmark). I try to upgrade to 5.7.3.1 another day.

I,m sorry to say, that I have got a new problem. I have upgradet to the newest version 5.7.5.8 in exactly the same way as you descriped to upgrade to 5.7.4.2.
But now I can't view my website. The adress ishttp://www.marieskiks.dk and when you go to the site, you get this message:
An exception occurred while executing 'select count(cID) from MultilingualSections': SQLSTATE[42S02]: Base table or view not found: 1146 Table 'marieskiks_dk_db.MultilingualSections' doesn't exist

What have I done wrong?

Fik du løst problemet..?? Og hvordan..??
Jeg har samme problem.

Hej. Ja, jeg fik løst problemet, men det var mildt sagt ikke nemt! Jeg mailede med en support på concrete5-danmark og efter en frem-og-tilbagemails kunne han konkludere, at det var et problem hos webhotellet (som er unoeuro). Så mailede jeg med deres support og så fik jeg løst problemet. Jeg har ikke så meget forstand på det, at jeg forstår det, emn forklaringen er, at deres webserver kører PHP7 hvilket åbenbart er en nyere "ting" end concrete5 kører med. Problemet løses sådan (copy-paste fra supportens svar):
Du kan løse det med det samme ved at indsætte:

AddType application/x-httpd-php-old .php

i bunden af din .htaccess fil (Filen SKAL hedde .htaccess, hvis filen ikke findes kan du blot oprette den).

Det vil nedgradere PHP til PHP 5.6, bemærk det er en midlertidig løsning og alle webhoteller vil blive tvunget op på PHP 7 på sigt. Det giver derfor god mening at nedgradere, løse problemet og så opgradere igen efterfølgende (ved at fjerne linjen). Så får du også gavn af fordelene ved PHP7.

Se nærmere her:http://blog.unoeuro.com/2015/12/php7-opgraderingsguide/...

Håber dette kan hjælpe dig.

Mange tak for dit svar. :)
Det hjalp.