Hello Marteta,
To download the plugin correctly you have to visit:
https://github.com/elliotcondon/acf/
And click the Zip button, then extract it and upload it to your plugins folder via FTP.
I also just tried to download the plugin using the download button, but it does not work, as mentioned in the description:
“Due to the new terms and conditions governing WordPress plugins, ACF has been relocated to github. This will allow the plugin to be accessible whilst the new version is being built.”
Hey, no problem mate!
There is a work around, where you just change it to available and it works.
